Method and apparatus for mobility management in wireless communication system

ABSTRACT

The present disclosure relates to method and apparatus for mobility management in wireless communication system. According to an embodiment of the present disclosure, a method performed by a wireless device in a wireless communication system comprises: receiving a first message comprising mobility commands of candidate target cells, each of the mobility commands being related to an index; receiving a second message comprising the index related to a first mobility command of a candidate target cell among the mobility commands, and a second mobility command of the candidate target cell; and updating the first mobility command based on the second mobility command.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. § 119 (e), this application claims the benefit ofKorean Patent Application No. 10-2019-0004052, filed on Jan. 11, 2019,the contents of which are all hereby incorporated by reference herein intheir entirety.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The present disclosure relates to method and apparatus for mobilitymanagement in wireless communication system.

Related Art

3rd generation partnership project (3GPP) long-term evolution (LTE) is atechnology for enabling high-speed packet communications. Many schemeshave been proposed for the LTE objective including those that aim toreduce user and provider costs, improve service quality, and expand andimprove coverage and system capacity. The 3GPP LTE requires reduced costper bit, increased service availability, flexible use of a frequencyband, a simple structure, an open interface, and adequate powerconsumption of a terminal as an upper-level requirement.

Work has started in international telecommunication union (ITU) and 3GPPto develop requirements and specifications for new radio (NR) systems.3GPP has to identify and develop the technology components needed forsuccessfully standardizing the new RAT timely satisfying both the urgentmarket needs, and the more long-term requirements set forth by the ITUradio communication sector (ITU-R) international mobiletelecommunications (IMT)-2020 process. Further, the NR should be able touse any spectrum band ranging at least up to 100 GHz that may be madeavailable for wireless communications even in a more distant future.

The NR targets a single technical framework addressing all usagescenarios, requirements and deployment scenarios including enhancedmobile broadband (eMBB), massive machine-type-communications (mMTC),ultra-reliable and low latency communications (URLLC), etc. The NR shallbe inherently forward compatible.

In a wireless communication system, a wireless device and/or userequipment (UE) may move along cells/base stations deployed in a widerange of areas. To provide proper services to the wireless device, thenetwork should manage a mobility of the wireless device, and thewireless device should perform a mobility to another cell according tothe mobility management. For example, the network may control a mobility(e.g., handover, SN change and/or SN addition) of the wireless device atarget cell. The wireless may need to receive mobility command(s) fromthe network, and apply the mobility command(s) to perform a mobility tothe target cell.

SUMMARY OF THE DISCLOSURE Technical Problem

An aspect of the present disclosure is to provide method and apparatusfor mobility management in a wireless communication system.

Another aspect of the present disclosure is to provide method andapparatus for delta configuration (i.e., configuration update) of RRCreconfiguration in a wireless communication system.

Yet another aspect of the present disclosure is to provide method andapparatus for signalling of the delta configuration in a wirelesscommunication system.

Yet another aspect of the present disclosure is to provide method andapparatus for delta configuration of mobility command in a mobilityprocedure in a wireless communication system.

Technical Solution

According to an embodiment of the present disclosure, a method performedby a wireless device in a wireless communication system comprises:receiving a first message comprising mobility commands of candidatetarget cells, each of the mobility commands being related to an index;receiving a second message comprising the index related to a firstmobility command of a candidate target cell among the mobility commands,and a second mobility command of the candidate target cell; and updatingthe first mobility command based on the second mobility command.

According to an embodiment of the present disclosure, a wireless devicein a wireless communication system comprises: a transceiver; a memory;and at least one processor operatively coupled to the transceiver andthe memory, and configured to: control the transceiver to receive afirst message comprising mobility commands of candidate target cells,each of the mobility commands being related to an index, control thetransceiver to receive a second message comprising the index related toa first mobility command of a candidate target cell among the mobilitycommands, and a second mobility command of the candidate target cell,and update the first mobility command based on the second mobilitycommand.

According to an embodiment of the present disclosure, a method performedby a radio access network (RAN) node in a wireless communication systemcomprises: transmitting a first message comprising mobility commands ofcandidate target cells, each of the mobility commands being related toan index; and transmitting a second message comprising the index relatedto a first mobility command of a candidate target cell among themobility commands, and a second mobility command of the candidate targetcell, wherein the second mobility command includes parameter values ofat least one first entry that are updated from those of the at least onefirst entry in the first mobility command, and excludes parameter valuesof at least one second entry that are included in the first mobilitycommand.

According to an embodiment of the present disclosure, a radio accessnetwork (RAN) node in a wireless communication system comprises: atransceiver; a memory; and at least one processor operatively coupled tothe transceiver and the memory, and configured to: control thetransceiver to transmit a first message comprising mobility commands ofcandidate target cells, each of the mobility commands being related toan index, and control the transceiver to transmit a second messagecomprising the index related to a first mobility command of a candidatetarget cell among the mobility commands, and a second mobility commandof the candidate target cell, wherein the second mobility commandincludes parameter values of at least one first entry that are updatedfrom those of the at least one first entry in the first mobilitycommand, and excludes parameter values of at least one second entry thatare included in the first mobility command.

According to an embodiment of the present disclosure, a processor for awireless device in a wireless communication system, wherein theprocessor is configured to control the wireless device to performoperations comprising: receiving a first message comprising mobilitycommands of candidate target cells, each of the mobility commands beingrelated to an index; receiving a second message comprising the indexrelated to a first mobility command of a candidate target cell among themobility commands, and a second mobility command of the candidate targetcell; and updating the first mobility command based on the secondmobility command.

According to an embodiment of the present disclosure, acomputer-readable medium having recorded thereon a program forperforming each step of a method on a computer, the method comprising:receiving a first message comprising mobility commands of candidatetarget cells, each of the mobility commands being related to an index;receiving a second message comprising the index related to a firstmobility command of a candidate target cell among the mobility commands,and a second mobility command of the candidate target cell; and updatingthe first mobility command based on the second mobility command.

Advantageous Effect

The present disclosure can have various advantageous effects.

For example, by transmitting an updated mobility command includingupdated configuration parameters and excluding configuration parametersincluded in a previously transmitted mobility command (i.e.,configuration parameters that are not updated or remain the same), thenetwork can send a mobility command of reduced sized to the wirelessdevice, in particular when multiple target cells are configured forconditional mobility.

For example, it is beneficial to reduce signalling overhead in case whenmultiple target cells are configured for conditional mobility or whenconditional mobility command is updated that the network transmits anupdated mobility command including updated configuration parameters andexcluding configuration parameters included in a previously transmittedmobility command (i.e., configuration parameters that are not updated orremain the same).

Advantageous effects which can be obtained through specific embodimentsof the present disclosure are not limited to the advantageous effectslisted above. For example, there may be a variety of technical effectsthat a person having ordinary skill in the related art can understandand/or derive from the present disclosure. Accordingly, the specificeffects of the present disclosure are not limited to those explicitlydescribed herein, but may include various effects that may be understoodor derived from the technical features of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows examples of 5G usage scenarios to which the technicalfeatures of the present disclosure can be applied.

FIG. 2 shows an example of a wireless communication system to which thetechnical features of the present disclosure can be applied.

FIG. 3 shows an example of a wireless communication system to which thetechnical features of the present disclosure can be applied.

FIG. 4 shows another example of a wireless communication system to whichthe technical features of the present disclosure can be applied.

FIG. 5 shows a block diagram of a user plane protocol stack to which thetechnical features of the present disclosure can be applied.

FIG. 6 shows a block diagram of a control plane protocol stack to whichthe technical features of the present disclosure can be applied.

FIG. 7 illustrates a frame structure in a 3GPP based wirelesscommunication system.

FIG. 8 illustrates a data flow example in the 3GPP NR system.

FIG. 9 shows an example of RRC reconfiguration procedure if the RRCreconfiguration is successful to which technical features of the presentdisclosure can be applied.

FIG. 10 shows an example of RRC reconfiguration procedure if the RRCreconfiguration fails to which technical features of the presentdisclosure can be applied.

FIG. 11 shows an example of a dual connectivity (DC) architecture towhich technical features of the present disclosure can be applied.

FIG. 12 shows an example of a conditional handover procedure to whichtechnical features of the present disclosure can be applied.

FIG. 13 shows an example of a method for mobility management accordingto an embodiment of the present disclosure.

FIG. 14 shows an example of a method to perform a mobility to a targetcell according to an embodiment of the present disclosure. The stepsillustrated in FIG. 14 may be performed by a wireless device and/or aUE.

FIG. 15 shows an example of a method for performing a mobility to atarget cell according to an embodiment of the present disclosure.

FIG. 16 shows an example of signal flows for updating a mobility commandin a mobility procedure according to an embodiment of the presentdisclosure.

FIG. 17 shows a UE to implement an embodiment of the present disclosure.The present disclosure described above for UE side may be applied tothis embodiment.

FIG. 18 shows another example of a wireless communication system towhich the technical features of the present disclosure can be applied.

FIG. 19 shows an example of an AI device to which the technical featuresof the present disclosure can be applied.

FIG. 20 shows an example of an AI system to which the technical featuresof the present disclosure can be applied.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The technical features described below may be used by a communicationstandard by the 3rd generation partnership project (3GPP)standardization organization, a communication standard by the instituteof electrical and electronics engineers (IEEE), etc. For example, thecommunication standards by the 3GPP standardization organization includelong-term evolution (LTE) and/or evolution of LTE systems. The evolutionof LTE systems includes LTE-advanced (LTE-A), LTE-A Pro, and/or 5G newradio (NR). The communication standard by the IEEE standardizationorganization includes a wireless local area network (WLAN) system suchas IEEE 802.11a/b/g/n/ac/ax. The above system uses various multipleaccess technologies such as orthogonal frequency division multipleaccess (OFDMA) and/or single carrier frequency division multiple access(SC-FDMA) for downlink (DL) and/or uplink (UL). For example, only OFDMAmay be used for DL and only SC-FDMA may be used for UL. Alternatively,OFDMA and SC-FDMA may be used for DL and/or UL.

In the present disclosure, “A or B” may mean “only A”, “only B”, or“both A and B”. In other words, “A or B” in the present disclosure maybe interpreted as “A and/or B”. For example, “A, B or C” in the presentdisclosure may mean “only A”, “only B”, “only C”, or “any combination ofA, B and C”.

In the present disclosure, slash (/) or comma (,) may mean “and/or”. Forexample, “A/B” may mean “A and/or B”. Accordingly, “A/B” may mean “onlyA”, “only B”, or “both A and B”. For example, “A, B, C” may mean “A, Bor C”.

In the present disclosure, “at least one of A and B” may mean “only A”,“only B” or “both A and B”. In addition, the expression “at least one ofA or B” or “at least one of A and/or B” in the present disclosure may beinterpreted as same as “at least one of A and B”.

In addition, in the present disclosure, “at least one of A, B and C” maymean “only A”, “only B”, “only C”, or “any combination of A, B and C”.In addition, “at least one of A, B or C” or “at least one of A, B and/orC” may mean “at least one of A, B and C”.

Also, parentheses used in the present disclosure may mean “for example”.In detail, when it is shown as “control information (PDCCH)”, “PDCCH”may be proposed as an example of “control information”. In other words,“control information” in the present disclosure is not limited to“PDCCH”, and “PDDCH” may be proposed as an example of “controlinformation”. In addition, even when shown as “control information(i.e., PDCCH)”, “PDCCH” may be proposed as an example of “controlinformation”.

Technical features that are separately described in one drawing in thepresent disclosure may be implemented separately or simultaneously.

The terms used throughout the disclosure can be defined as thefollowings:

‘Mobility’ refers to a procedure for i) changing a PCell of a UE (i.e.,handover or PCell change), ii) changing a PSCell of a UE (i.e., SNchange or PSCell change), and/or iii) adding a PSCell for a UE (i.e., SNaddition or PSCell addition). Therefore, the mobility may comprise atleast one of a handover, an SN change or an SN addition. In other words,the mobility may comprise at least one of PCell change, PSCell change orPSCell addition. Throughout the disclosure, performing a mobility to atarget cell may refer to applying a mobility command of the target cellor applying RRC reconfiguration parameters in the mobility command ofthe target cell. Further, RRC reconfiguration and RRC connectionreconfiguration may be used interchangeably.

‘SN mobility’ refers to a procedure for i) changing a PSCell of a UE(i.e., SN change or PSCell change), and/or ii) adding a PSCell for a UE(i.e., SN addition or PSCell addition). Therefore, the SN mobility maycomprise at least one of an SN change or an SN addition. In other words,the SN mobility may comprise at least one of PSCell change or PSCelladdition. Throughout the disclosure, performing an SN mobility to atarget cell may refer to applying an SN mobility command of the targetcell or applying RRC reconfiguration parameters in the SN mobilitycommand of the target cell. The SN mobility may be a kind of a mobility.The SN mobility command may comprise a SN change command for performingSN change, or SN addition command for performing SN addition.

‘Mobility condition for a target cell’ refers to a triggering conditionfor a mobility to the target cell. That is, the mobility condition for atarget cell refers to a condition that should be satisfied fortriggering a mobility to the target cell. Mobility condition maycomprise at least one of an event, time-to-trigger (TTT), offset value,or threshold value(s). The mobility condition for an event may besatisfied if an entering condition for the event is satisfied for atleast the TTT. For example, the entering condition for event A3 may besatisfied if a signal quality for a target cell is better than that fora source cell more than or equal to the offset value. For anotherexample, the entering condition for event A5 may be satisfied if asignal quality for a target cell is better than a first threshold and asignal quality for a source cell is lower than a second threshold.

‘SN mobility condition for a target cell’ refers to a triggeringcondition for an SN mobility (i.e., SN addition or SN change) to thetarget cell. That is, the SN mobility condition for a target cell refersto a condition that should be satisfied for triggering an SN mobility tothe target cell. SN mobility condition for a target cell may beclassified as:

i) SN addition condition for a target cell, which refers to a triggeringcondition for an SN addition of the target cell; or

ii) SN change condition for a target cell, which refers to a triggeringcondition for an SN change to the target cell.

SN mobility condition may comprise at least one of an event,time-to-trigger (TTT), offset value, or threshold value(s). The SNmobility condition for an event may be satisfied if an enteringcondition for the event is satisfied for at least the TTT.

For example, SN addition condition may be related to event A4 or eventB1. The entering condition for event A4 or B1 may be satisfied if asignal quality for a target cell is better than a threshold.

For example, SN change condition may be related to event A3 or event A5.The entering condition for event A3 may be satisfied if a signal qualityfor a target cell is better than that for a source PScell more than orequal to the offset value. For another example, the entering conditionfor event A5 may be satisfied if a signal quality for a target cell isbetter than a first threshold and a signal quality for a source PScellis lower than a second threshold.

‘Conditional mobility’ refers to a mobility that is performed to atarget cell which satisfies a triggering condition among a plurality ofcandidate target cells. Throughout the disclosure, performing aconditional mobility to a target cell may refer to applying aconditional mobility command of a target cell which satisfies a mobilitycondition for the target cell among a plurality of candidate targetcells or applying RRC reconfiguration parameters in the conditionalmobility command of the target cell which satisfies a mobility conditionfor the target cell among the plurality of candidate target cells.

Throughout the disclosure, the terms ‘radio access network (RAN) node’,‘base station’, ‘eNB’, ‘gNB’ and ‘cell’ may be used interchangeably.Further, a UE may be a kind of a wireless device, and throughout thedisclosure, the terms ‘UE’ and ‘wireless device’ may be usedinterchangeably.

The following drawings are created to explain specific embodiments ofthe present disclosure. The names of the specific devices or the namesof the specific signals/messages/fields shown in the drawings areprovided by way of example, and thus the technical features of thepresent disclosure are not limited to the specific names used in thefollowing drawings.

FIG. 1 shows examples of 5G usage scenarios to which the technicalfeatures of the present disclosure can be applied.

The 5G usage scenarios shown in FIG. 1 are only exemplary, and thetechnical features of the present disclosure can be applied to other 5Gusage scenarios which are not shown in FIG. 1.

Referring to FIG. 1, the three main requirements areas of 5G include (1)enhanced mobile broadband (eMBB) domain, (2) massive machine typecommunication (mMTC) area, and (3) ultra-reliable and low latencycommunications (URLLC) area. Some use cases may require multiple areasfor optimization and, other use cases may only focus on only one keyperformance indicator (KPI). 5G is to support these various use cases ina flexible and reliable way.

eMBB focuses on across-the-board enhancements to the data rate, latency,user density, capacity and coverage of mobile broadband access. The eMBBaims ˜10 Gbps of throughput. eMBB far surpasses basic mobile Internetaccess and covers rich interactive work and media and entertainmentapplications in cloud and/or augmented reality. Data is one of the keydrivers of 5G and may not be able to see dedicated voice services forthe first time in the 5G era. In 5G, the voice is expected to beprocessed as an application simply using the data connection provided bythe communication system. The main reason for the increased volume oftraffic is an increase in the size of the content and an increase in thenumber of applications requiring high data rates. Streaming services(audio and video), interactive video and mobile Internet connectivitywill become more common as more devices connect to the Internet. Many ofthese applications require always-on connectivity to push real-timeinformation and notifications to the user. Cloud storage andapplications are growing rapidly in mobile communication platforms,which can be applied to both work and entertainment. Cloud storage is aspecial use case that drives growth of uplink data rate. 5G is also usedfor remote tasks on the cloud and requires much lower end-to-end delayto maintain a good user experience when the tactile interface is used.In entertainment, for example, cloud games and video streaming areanother key factor that increases the demand for mobile broadbandcapabilities. Entertainment is essential in smartphones and tabletsanywhere, including high mobility environments such as trains, cars andairplanes. Another use case is augmented reality and informationretrieval for entertainment. Here, augmented reality requires very lowlatency and instantaneous data amount.

mMTC is designed to enable communication between devices that arelow-cost, massive in number and battery-driven, intended to supportapplications such as smart metering, logistics, and field and bodysensors. mMTC aims ˜10 years on battery and/or ˜1 million devices/km2.mMTC allows seamless integration of embedded sensors in all areas and isone of the most widely used 5G applications. Potentially by 2020,internet-of-things (IoT) devices are expected to reach 20.4 billion.Industrial IoT is one of the areas where 5G plays a key role in enablingsmart cities, asset tracking, smart utilities, agriculture and securityinfrastructures.

URLLC will make it possible for devices and machines to communicate withultra-reliability, very low latency and high availability, making itideal for vehicular communication, industrial control, factoryautomation, remote surgery, smart grids and public safety applications.URLLC aims ˜1 ms of latency. URLLC includes new services that willchange the industry through links with ultra-reliability/low latency,such as remote control of key infrastructure and self-driving vehicles.The level of reliability and latency is essential for smart gridcontrol, industrial automation, robotics, drones control andcoordination.

Next, a plurality of use cases included in the triangle of FIG. 1 willbe described in more detail.

5G can complement fiber-to-the-home (FTTH) and cable-based broadband (orDOCSIS) as a means of delivering streams rated from hundreds of megabitsper second to gigabits per second. This high speed can be required todeliver TVs with resolutions of 4K or more (6K, 8K and above) as well asvirtual reality (VR) and augmented reality (AR). VR and AR applicationsinclude mostly immersive sporting events. Certain applications mayrequire special network settings. For example, in the case of a VR game,a game company may need to integrate a core server with an edge networkserver of a network operator to minimize delay.

Automotive is expected to become an important new driver for 5G, withmany use cases for mobile communications to vehicles. For example,entertainment for passengers demands high capacity and high mobilebroadband at the same time. This is because future users will continueto expect high-quality connections regardless of their location andspeed. Another use case in the automotive sector is an augmented realitydashboard. The driver can identify an object in the dark on top of whatis being viewed through the front window through the augmented realitydashboard. The augmented reality dashboard displays information thatwill inform the driver about the object's distance and movement. In thefuture, the wireless module enables communication between vehicles,information exchange between the vehicle and the supportinginfrastructure, and information exchange between the vehicle and otherconnected devices (e.g. devices accompanied by a pedestrian). The safetysystem allows the driver to guide the alternative course of action sothat he can drive more safely, thereby reducing the risk of accidents.The next step will be a remotely controlled vehicle or self-drivingvehicle. This requires a very reliable and very fast communicationbetween different self-driving vehicles and between vehicles andinfrastructure. In the future, a self-driving vehicle will perform alldriving activities, and the driver will focus only on traffic that thevehicle itself cannot identify. The technical requirements ofself-driving vehicles require ultra-low latency and high-speedreliability to increase traffic safety to a level not achievable byhumans.

Smart cities and smart homes, which are referred to as smart societies,will be embedded in high density wireless sensor networks. Thedistributed network of intelligent sensors will identify conditions forcost and energy-efficient maintenance of a city or house. A similarsetting can be performed for each home. Temperature sensors, windows andheating controllers, burglar alarms and appliances are all wirelesslyconnected. Many of these sensors typically require low data rate, lowpower and low cost. However, for example, real-time high-definition (HD)video may be required for certain types of devices for monitoring.

The consumption and distribution of energy, including heat or gas, ishighly dispersed, requiring automated control of distributed sensornetworks. The smart grid interconnects these sensors using digitalinformation and communication technologies to collect and act oninformation. This information can include supplier and consumerbehavior, allowing the smart grid to improve the distribution of fuel,such as electricity, in terms of efficiency, reliability, economy,production sustainability, and automated methods. The smart grid can beviewed as another sensor network with low latency.

The health sector has many applications that can benefit from mobilecommunications. Communication systems can support telemedicine toprovide clinical care in remote locations. This can help to reducebarriers to distance and improve access to health services that are notcontinuously available in distant rural areas. It is also used to savelives in critical care and emergency situations. Mobile communicationbased wireless sensor networks can provide remote monitoring and sensorsfor parameters such as heart rate and blood pressure.

Wireless and mobile communications are becoming increasingly importantin industrial applications. Wiring costs are high for installation andmaintenance. Thus, the possibility of replacing a cable with a wirelesslink that can be reconfigured is an attractive opportunity in manyindustries. However, achieving this requires that wireless connectionsoperate with similar delay, reliability, and capacity as cables and thattheir management is simplified. Low latency and very low errorprobabilities are new requirements that need to be connected to 5G.

Logistics and freight tracking are important use cases of mobilecommunications that enable tracking of inventory and packages anywhereusing location based information systems. Use cases of logistics andfreight tracking typically require low data rates, but require a largerange and reliable location information.

NR supports multiple numerology (or, subcarrier spacing (SCS)) tosupport various 5G services. For example, when the SCS is 15 kHz, widearea in traditional cellular bands may be supported. When the SCS is 30kHz/60 kHz, dense-urban, lower latency and wider carrier bandwidth maybe supported. When the SCS is 60 kHz or higher, a bandwidth greater than24.25 GHz may be supported to overcome phase noise.

The NR frequency band may be defined as two types of frequency range,i.e., FR1 and FR2. The numerical value of the frequency range may bechanged. For example, the frequency ranges of the two types (FR1 andFR2) may be as shown in Table 1 below. For ease of explanation, in thefrequency ranges used in the NR system, FR1 may mean “sub 6 GHz range”,FR2 may mean “above 6 GHz range,” and may be referred to as millimeterwave (mmW).

TABLE 1 Frequency Range Corresponding frequency designation rangeSubcarrier Spacing FR1  450 MHz-6000 MHz 15, 30, 60 kHz FR2 24250MHz-52600 MHz 60, 120, 240 kHz

As mentioned above, the numerical value of the frequency range of the NRsystem may be changed. For example, FR1 may include a frequency band of410 MHz to 7125 MHz as shown in Table 2 below. That is, FR1 may includea frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or more. Forexample, a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) ormore included in FR1 may include an unlicensed band. Unlicensed bandsmay be used for a variety of purposes, for example for communication forvehicles (e.g., autonomous driving).

TABLE 2 Frequency Range Corresponding frequency designation rangeSubcarrier Spacing FR1  410 MHz-7125 MHz 15, 30, 60 kHz FR2 24250MHz-52600 MHz 60, 120, 240 kHz

FIG. 2 shows an example of a wireless communication system to which thetechnical features of the present disclosure can be applied.

Referring to FIG. 2, the wireless communication system may include afirst device 210 and a second device 220.

The first device 210 includes a base station, a network node, atransmitting UE, a receiving UE, a wireless device, a wirelesscommunication device, a vehicle, a vehicle equipped with an autonomousdriving function, a connected car, a drone, an unmanned aerial vehicle(UAV), an artificial intelligence (AI) module, a robot, an AR device, aVR device, a mixed reality (MR) device, a hologram device, a publicsafety device, an MTC device, an IoT device, a medical device, afin-tech device (or, a financial device), a security device, aclimate/environmental device, a device related to 5G services, or adevice related to the fourth industrial revolution.

The second device 220 includes a base station, a network node, atransmitting UE, a receiving UE, a wireless device, a wirelesscommunication device, a vehicle, a vehicle equipped with an autonomousdriving function, a connected car, a drone, a UAV, an AI module, arobot, an AR device, a VR device, an MR device, a hologram device, apublic safety device, an MTC device, an IoT device, a medical device, afin-tech device (or, a financial device), a security device, aclimate/environmental device, a device related to 5G services, or adevice related to the fourth industrial revolution.

For example, the UE may include a mobile phone, a smart phone, a laptopcomputer, a digital broadcasting terminal, a personal digital assistant(PDA), a portable multimedia player (PMP), a navigation device, a slatepersonal computer (PC), a tablet PC, an ultrabook, a wearable device(e.g. a smartwatch, a smart glass, a head mounted display (HMD)). Forexample, the HMD may be a display device worn on the head. For example,the HMD may be used to implement AR, VR and/or MR.

For example, the drone may be a flying object that is flying by a radiocontrol signal without a person boarding it. For example, the VR devicemay include a device that implements an object or background in thevirtual world. For example, the AR device may include a device thatimplements connection of an object and/or a background of a virtualworld to an object and/or a background of the real world. For example,the MR device may include a device that implements fusion of an objectand/or a background of a virtual world to an object and/or a backgroundof the real world. For example, the hologram device may include a devicethat implements a 360-degree stereoscopic image by recording and playingstereoscopic information by utilizing a phenomenon of interference oflight generated by the two laser lights meeting with each other, calledholography. For example, the public safety device may include a videorelay device or a video device that can be worn by the user's body. Forexample, the MTC device and the IoT device may be a device that do notrequire direct human intervention or manipulation. For example, the MTCdevice and the IoT device may include a smart meter, a vending machine,a thermometer, a smart bulb, a door lock and/or various sensors. Forexample, the medical device may be a device used for the purpose ofdiagnosing, treating, alleviating, handling, or preventing a disease.For example, the medical device may be a device used for the purpose ofdiagnosing, treating, alleviating, or correcting an injury or disorder.For example, the medical device may be a device used for the purpose ofinspecting, replacing or modifying a structure or function. For example,the medical device may be a device used for the purpose of controllingpregnancy. For example, the medical device may include a treatmentdevice, a surgical device, an (in vitro) diagnostic device, a hearingaid and/or a procedural device, etc. For example, a security device maybe a device installed to prevent the risk that may occur and to maintainsafety. For example, the security device may include a camera, aclosed-circuit TV (CCTV), a recorder, or a black box. For example, thefin-tech device may be a device capable of providing financial servicessuch as mobile payment. For example, the fin-tech device may include apayment device or a point of sales (POS). For example, theclimate/environmental device may include a device for monitoring orpredicting the climate/environment.

The first device 210 may include at least one or more processors, suchas a processor 211, at least one memory, such as a memory 212, and atleast one transceiver, such as a transceiver 213. The processor 211 mayperform the functions, procedures, and/or methods of the first devicedescribed throughout the disclosure. The processor 211 may perform oneor more protocols. For example, the processor 211 may perform one ormore layers of the air interface protocol. The memory 212 is connectedto the processor 211 and may store various types of information and/orinstructions. The transceiver 213 is connected to the processor 211 andmay be controlled by the processor 211 to transmit and receive wirelesssignals.

The second device 220 may include at least one or more processors, suchas a processor 221, at least one memory, such as a memory 222, and atleast one transceiver, such as a transceiver 223. The processor 221 mayperform the functions, procedures, and/or methods of the second device220 described throughout the disclosure. The processor 221 may performone or more protocols. For example, the processor 221 may perform one ormore layers of the air interface protocol. The memory 222 is connectedto the processor 221 and may store various types of information and/orinstructions. The transceiver 223 is connected to the processor 221 andmay be controlled by the processor 221 to transmit and receive wirelesssignals.

The memory 212, 222 may be connected internally or externally to theprocessor 211, 212, or may be connected to other processors via avariety of technologies such as wired or wireless connections.

The first device 210 and/or the second device 220 may have more than oneantenna. For example, antenna 214 and/or antenna 224 may be configuredto transmit and receive wireless signals.

FIG. 3 shows an example of a wireless communication system to which thetechnical features of the present disclosure can be applied.

Specifically, FIG. 3 shows a system architecture based on anevolved-UMTS terrestrial radio access network (E-UTRAN). Theaforementioned LTE is a part of an evolved-UTMS (e-UMTS) using theE-UTRAN.

Referring to FIG. 3, the wireless communication system includes one ormore user equipment (UE) 310, an E-UTRAN and an evolved packet core(EPC). The UE 310 refers to a communication equipment carried by a user.The UE 310 may be fixed or mobile. The UE 310 may be referred to asanother terminology, such as a mobile station (MS), a user terminal(UT), a subscriber station (SS), a wireless device, etc.

The E-UTRAN consists of one or more evolved NodeB (eNB) 320. The eNB 320provides the E-UTRA user plane and control plane protocol terminationstowards the UE 10. The eNB 320 is generally a fixed station thatcommunicates with the UE 310. The eNB 320 hosts the functions, such asinter-cell radio resource management (RRM), radio bearer (RB) control,connection mobility control, radio admission control, measurementconfiguration/provision, dynamic resource allocation (scheduler), etc.The eNB 320 may be referred to as another terminology, such as a basestation (BS), a base transceiver system (BTS), an access point (AP),etc.

A downlink (DL) denotes communication from the eNB 320 to the UE 310. Anuplink (UL) denotes communication from the UE 310 to the eNB 320. Asidelink (SL) denotes communication between the UEs 310. In the DL, atransmitter may be a part of the eNB 320, and a receiver may be a partof the UE 310. In the UL, the transmitter may be a part of the UE 310,and the receiver may be a part of the eNB 320. In the SL, thetransmitter and receiver may be a part of the UE 310.

The EPC includes a mobility management entity (MME), a serving gateway(S-GW) and a packet data network (PDN) gateway (P-GW). The MME hosts thefunctions, such as non-access stratum (NAS) security, idle statemobility handling, evolved packet system (EPS) bearer control, etc. TheS-GW hosts the functions, such as mobility anchoring, etc. The S-GW is agateway having an E-UTRAN as an endpoint. For convenience, MME/S-GW 330will be referred to herein simply as a “gateway,” but it is understoodthat this entity includes both the MME and S-GW. The P-GW hosts thefunctions, such as UE Internet protocol (IP) address allocation, packetfiltering, etc. The P-GW is a gateway having a PDN as an endpoint. TheP-GW is connected to an external network.

The UE 310 is connected to the eNB 320 by means of the Uu interface. TheUEs 310 are interconnected with each other by means of the PC5interface. The eNBs 320 are interconnected with each other by means ofthe X2 interface. The eNBs 320 are also connected by means of the S1interface to the EPC, more specifically to the MME by means of theS1-MME interface and to the S-GW by means of the S1-U interface. The S1interface supports a many-to-many relation between MMES/S-GWs and eNBs.

FIG. 4 shows another example of a wireless communication system to whichthe technical features of the present disclosure can be applied.

Specifically, FIG. 4 shows a system architecture based on a 5G NR. Theentity used in the 5G NR (hereinafter, simply referred to as “NR”) mayabsorb some or all of the functions of the entities introduced in FIG. 3(e.g. eNB, MME, S-GW). The entity used in the NR may be identified bythe name “NG” for distinction from the LTE/LTE-A.

Referring to FIG. 4, the wireless communication system includes one ormore UE 410, a next-generation RAN (NG-RAN) and a 5th generation corenetwork (5GC). The NG-RAN consists of at least one NG-RAN node. TheNG-RAN node is an entity corresponding to the eNB 320 shown in FIG. 3.The NG-RAN node consists of at least one gNB 421 and/or at least oneng-eNB 422. The gNB 421 provides NR user plane and control planeprotocol terminations towards the UE 410. The ng-eNB 422 provides E-UTRAuser plane and control plane protocol terminations towards the UE 410.

The 5GC includes an access and mobility management function (AMF), auser plane function (UPF) and a session management function (SMF). TheAMF hosts the functions, such as NAS security, idle state mobilityhandling, etc. The AMF is an entity including the functions of theconventional MME. The UPF hosts the functions, such as mobilityanchoring, protocol data unit (PDU) handling. The UPF an entityincluding the functions of the conventional S-GW. The SMF hosts thefunctions, such as UE IP address allocation, PDU session control.

The gNBs 421 and ng-eNBs 422 are interconnected with each other by meansof the Xn interface. The gNBs 421 and ng-eNBs 422 are also connected bymeans of the NG interfaces to the 5GC, more specifically to the AMF bymeans of the NG-C interface and to the UPF by means of the NG-Uinterface.

A protocol structure between network entities described above isdescribed. On the system of FIG. 3 and/or FIG. 4, layers of a radiointerface protocol between the UE and the network (e.g. NG-RAN and/orE-UTRAN) may be classified into a first layer (L1), a second layer (L2),and a third layer (L3) based on the lower three layers of the opensystem interconnection (OSI) model that is well-known in thecommunication system.

FIG. 5 shows a block diagram of a user plane protocol stack to which thetechnical features of the present disclosure can be applied. FIG. 6shows a block diagram of a control plane protocol stack to which thetechnical features of the present disclosure can be applied.

The user/control plane protocol stacks shown in FIG. 5 and FIG. 6 areused in NR. However, user/control plane protocol stacks shown in FIG. 5and FIG. 6 may be used in LTE/LTE-A without loss of generality, byreplacing gNB/AMF with eNB/MME.

Referring to FIG. 5 and FIG. 6, a physical (PHY) layer belonging to L1.The PHY layer offers information transfer services to media accesscontrol (MAC) sublayer and higher layers. The PHY layer offers to theMAC sublayer transport channels. Data between the MAC sublayer and thePHY layer is transferred via the transport channels. Between differentPHY layers, i.e., between a PHY layer of a transmission side and a PHYlayer of a reception side, data is transferred via the physicalchannels.

The MAC sublayer belongs to L2. The main services and functions of theMAC sublayer include mapping between logical channels and transportchannels, multiplexing/de-multiplexing of MAC service data units (SDUs)belonging to one or different logical channels into/from transportblocks (TB) delivered to/from the physical layer on transport channels,scheduling information reporting, error correction through hybridautomatic repeat request (HARM), priority handling between UEs by meansof dynamic scheduling, priority handling between logical channels of oneUE by means of logical channel prioritization (LCP), etc. The MACsublayer offers to the radio link control (RLC) sublayer logicalchannels.

The RLC sublayer belong to L2. The RLC sublayer supports threetransmission modes, i.e. transparent mode (TM), unacknowledged mode(UM), and acknowledged mode (AM), in order to guarantee various qualityof services (QoS) required by radio bearers. The main services andfunctions of the RLC sublayer depend on the transmission mode. Forexample, the RLC sublayer provides transfer of upper layer PDUs for allthree modes, but provides error correction through ARQ for AM only. InLTE/LTE-A, the RLC sublayer provides concatenation, segmentation andreassembly of RLC SDUs (only for UM and AM data transfer) andre-segmentation of RLC data PDUs (only for AM data transfer). In NR, theRLC sublayer provides segmentation (only for AM and UM) andre-segmentation (only for AM) of RLC SDUs and reassembly of SDU (onlyfor AM and UM). That is, the NR does not support concatenation of RLCSDUs. The RLC sublayer offers to the packet data convergence protocol(PDCP) sublayer RLC channels.

The PDCP sublayer belong to L2. The main services and functions of thePDCP sublayer for the user plane include header compression anddecompression, transfer of user data, duplicate detection, PDCP PDUrouting, retransmission of PDCP SDUs, ciphering and deciphering, etc.The main services and functions of the PDCP sublayer for the controlplane include ciphering and integrity protection, transfer of controlplane data, etc.

The service data adaptation protocol (SDAP) sublayer belong to L2. TheSDAP sublayer is only defined in the user plane. The SDAP sublayer isonly defined for NR. The main services and functions of SDAP include,mapping between a QoS flow and a data radio bearer (DRB), and markingQoS flow ID (QFI) in both DL and UL packets. The SDAP sublayer offers to5GC QoS flows.

A radio resource control (RRC) layer belongs to L3. The RRC layer isonly defined in the control plane. The RRC layer controls radioresources between the UE and the network. To this end, the RRC layerexchanges RRC messages between the UE and the BS. The main services andfunctions of the RRC layer include broadcast of system informationrelated to AS and NAS, paging, establishment, maintenance and release ofan RRC connection between the UE and the network, security functionsincluding key management, establishment, configuration, maintenance andrelease of radio bearers, mobility functions, QoS management functions,UE measurement reporting and control of the reporting, NAS messagetransfer to/from NAS from/to UE.

In other words, the RRC layer controls logical channels, transportchannels, and physical channels in relation to the configuration,reconfiguration, and release of radio bearers. A radio bearer refers toa logical path provided by L (PHY layer) and L2 (MAC/RLC/PDCP/SDAPsublayer) for data transmission between a UE and a network. Setting theradio bearer means defining the characteristics of the radio protocollayer and the channel for providing a specific service, and setting eachspecific parameter and operation method. Radio bearer may be dividedinto signaling RB (SRB) and data RB (DRB). The SRB is used as a path fortransmitting RRC messages in the control plane, and the DRB is used as apath for transmitting user data in the user plane.

An RRC state indicates whether an RRC layer of the UE is logicallyconnected to an RRC layer of the E-UTRAN. In LTE/LTE-A, when the RRCconnection is established between the RRC layer of the UE and the RRClayer of the E-UTRAN, the UE is in the RRC connected state(RRC_CONNECTED). Otherwise, the UE is in the RRC idle state (RRC_IDLE).In NR, the RRC inactive state (RRC_INACTIVE) is additionally introduced.RRC_INACTIVE may be used for various purposes. For example, the massivemachine type communications (MMTC) UEs can be efficiently managed inRRC_INACTIVE. When a specific condition is satisfied, transition is madefrom one of the above three states to the other.

A predetermined operation may be performed according to the RRC state.In RRC_IDLE, public land mobile network (PLMN) selection, broadcast ofsystem information (SI), cell re-selection mobility, core network (CN)paging and discontinuous reception (DRX) configured by NAS may beperformed. The UE shall have been allocated an identifier (ID) whichuniquely identifies the UE in a tracking area. No RRC context stored inthe BS.

In RRC_CONNECTED, the UE has an RRC connection with the network (i.e.E-UTRAN/NG-RAN). Network-CN connection (both C/U-planes) is alsoestablished for UE. The UE AS context is stored in the network and theUE. The RAN knows the cell which the UE belongs to. The network cantransmit and/or receive data to/from UE. Network controlled mobilityincluding measurement is also performed.

Most of operations performed in RRC_IDLE may be performed inRRC_INACTIVE. But, instead of CN paging in RRC_IDLE, RAN paging isperformed in RRC_INACTIVE. In other words, in RRC_IDLE, paging formobile terminated (MT) data is initiated by core network and paging areais managed by core network. In RRC_INACTIVE, paging is initiated byNG-RAN, and RAN-based notification area (RNA) is managed by NG-RAN.Further, instead of DRX for CN paging configured by NAS in RRC_IDLE, DRXfor RAN paging is configured by NG-RAN in RRC_INACTIVE. Meanwhile, inRRC_INACTIVE, 5GC-NG-RAN connection (both C/U-planes) is established forUE, and the UE AS context is stored in NG-RAN and the UE. NG-RAN knowsthe RNA which the UE belongs to.

NAS layer is located at the top of the RRC layer. The NAS controlprotocol performs the functions, such as authentication, mobilitymanagement, security control.

The physical channels may be modulated according to OFDM processing andutilizes time and frequency as radio resources. The physical channelsconsist of a plurality of orthogonal frequency division multiplexing(OFDM) symbols in time domain and a plurality of subcarriers infrequency domain. One subframe consists of a plurality of OFDM symbolsin the time domain. A resource block is a resource allocation unit, andconsists of a plurality of OFDM symbols and a plurality of subcarriers.In addition, each subframe may use specific subcarriers of specific OFDMsymbols (e.g. first OFDM symbol) of the corresponding subframe for aphysical downlink control channel (PDCCH), i.e. L1/L2 control channel. Atransmission time interval (TTI) is a basic unit of time used by ascheduler for resource allocation. The TTI may be defined in units ofone or a plurality of slots, or may be defined in units of mini-slots.

The transport channels are classified according to how and with whatcharacteristics data are transferred over the radio interface. DLtransport channels include a broadcast channel (BCH) used fortransmitting system information, a downlink shared channel (DL-SCH) usedfor transmitting user traffic or control signals, and a paging channel(PCH) used for paging a UE. UL transport channels include an uplinkshared channel (UL-SCH) for transmitting user traffic or control signalsand a random access channel (RACH) normally used for initial access to acell.

Different kinds of data transfer services are offered by MAC sublayer.Each logical channel type is defined by what type of information istransferred. Logical channels are classified into two groups: controlchannels and traffic channels.

Control channels are used for the transfer of control plane informationonly. The control channels include a broadcast control channel (BCCH), apaging control channel (PCCH), a common control channel (CCCH) and adedicated control channel (DCCH). The BCCH is a DL channel forbroadcasting system control information. The PCCH is DL channel thattransfers paging information, system information change notifications.The CCCH is a channel for transmitting control information between UEsand network. This channel is used for UEs having no RRC connection withthe network. The DCCH is a point-to-point bi-directional channel thattransmits dedicated control information between a UE and the network.This channel is used by UEs having an RRC connection.

Traffic channels are used for the transfer of user plane informationonly. The traffic channels include a dedicated traffic channel (DTCH).The DTCH is a point-to-point channel, dedicated to one UE, for thetransfer of user information. The DTCH can exist in both UL and DL.

Regarding mapping between the logical channels and transport channels,in DL, BCCH can be mapped to BCH, BCCH can be mapped to DL-SCH, PCCH canbe mapped to PCH, CCCH can be mapped to DL-SCH, DCCH can be mapped toDL-SCH, and DTCH can be mapped to DL-SCH. In UL, CCCH can be mapped toUL-SCH, DCCH can be mapped to UL-SCH, and DTCH can be mapped to UL-SCH.

FIG. 7 illustrates a frame structure in a 3GPP based wirelesscommunication system.

The frame structure illustrated in FIG. 7 is purely exemplary and thenumber of subframes, the number of slots, and/or the number of symbolsin a frame may be variously changed. In the 3GPP based wirelesscommunication system, an OFDM numerology (e.g., subcarrier spacing(SCS), transmission time interval (TTI) duration) may be differentlyconfigured between a plurality of cells aggregated for one UE. Forexample, if a UE is configured with different SCSs for cells aggregatedfor the cell, an (absolute time) duration of a time resource (e.g. asubframe, a slot, or a TTI) including the same number of symbols may bedifferent among the aggregated cells. Herein, symbols may include OFDMsymbols (or CP-OFDM symbols), SC-FDMA symbols (or discrete Fouriertransform-spread-OFDM (DFT-s-OFDM) symbols).

Referring to FIG. 7, downlink and uplink transmissions are organizedinto frames. Each frame has Tf=10 ms duration. Each frame is dividedinto two half-frames, where each of the half-frames has 5 ms duration.Each half-frame consists of 5 subframes, where the duration Tsf persubframe is 1 ms. Each subframe is divided into slots and the number ofslots in a subframe depends on a subcarrier spacing. Each slot includes14 or 12 OFDM symbols based on a cyclic prefix (CP). In a normal CP,each slot includes 14 OFDM symbols and, in an extended CP, each slotincludes 12 OFDM symbols. The numerology is based on exponentiallyscalable subcarrier spacing Δf=2u*15 kHz. The following table shows thenumber of OFDM symbols per slot, the number of slots per frame, and thenumber of slots per for the normal CP, according to the subcarrierspacing Δf=2u*15 kHz.

TABLE 3 u Nslotsymb Nframe, uslot Nsubframe, uslot 0 14 10 1 1 14 20 2 214 40 4 3 14 80 8 u Nslotsymb Nframe, uslot Nsubframe, uslot 4 14 160 16 

The following table shows the number of OFDM symbols per slot, thenumber of slots per frame, and the number of slots per for the extendedCP, according to the subcarrier spacing Δf=2u*15 kHz.

TABLE 4 u Nslotsymb Nframe, uslot Nsubframe, uslot 2 12 40 4

A slot includes plural symbols (e.g., 14 or 12 symbols) in the timedomain. For each numerology (e.g. subcarrier spacing) and carrier, aresource grid of Nsize,ugrid,x*NRBsc subcarriers and Nsubframe,usymbOFDM symbols is defined, starting at common resource block (CRB)Nstart,ugrid indicated by higher-layer signaling (e.g. radio resourcecontrol (RRC) signaling), where Nsize,ugrid,x is the number of resourceblocks (RBs) in the resource grid and the subscript x is DL for downlinkand UL for uplink. NRBsc is the number of subcarriers per RB. In the3GPP based wireless communication system, NRBsc is 12 generally. Thereis one resource grid for a given antenna port p, subcarrier spacingconfiguration u, and transmission direction (DL or UL). The carrierbandwidth Nsize,ugrid for subcarrier spacing configuration u is given bythe higher-layer parameter (e.g. RRC parameter). Each element in theresource grid for the antenna port p and the subcarrier spacingconfiguration u is referred to as a resource element (RE) and onecomplex symbol may be mapped to each RE. Each RE in the resource grid isuniquely identified by an index k in the frequency domain and an index 1representing a symbol location relative to a reference point in the timedomain. In the 3GPP based wireless communication system, an RB isdefined by 12 consecutive subcarriers in the frequency domain.

In the 3GPP NR system, RBs are classified into CRBs and physicalresource blocks (PRBs). CRBs are numbered from 0 and upwards in thefrequency domain for subcarrier spacing configuration u. The center ofsubcarrier 0 of CRB 0 for subcarrier spacing configuration u coincideswith ‘point A’ which serves as a common reference point for resourceblock grids. In the 3GPP NR system, PRBs are defined within a bandwidthpart (BWP) and numbered from 0 to NsizeBWP,i−1, where i is the number ofthe bandwidth part. The relation between the physical resource blocknPRB in the bandwidth part i and the common resource block nCRB is asfollows: nPRB=nCRB+NsizeBWP,i, where NsizeBWP,i is the common resourceblock where bandwidth part starts relative to CRB 0. The BWP includes aplurality of consecutive RBs. A carrier may include a maximum of N(e.g., 5) BWPs. A UE may be configured with one or more BWPs on a givencomponent carrier. Only one BWP among BWPs configured to the UE canactive at a time. The active BWP defines the UE's operating bandwidthwithin the cell's operating bandwidth.

In the present disclosure, the term “cell” may refer to a geographicarea to which one or more nodes provide a communication system, or referto radio resources. A “cell” of a geographic area may be understood ascoverage within which a node can provide service using a carrier and a“cell” as radio resources (e.g. time-frequency resources) is associatedwith bandwidth (BW) which is a frequency range configured by thecarrier. The “cell” associated with the radio resources is defined by acombination of downlink resources and uplink resources, for example, acombination of a downlink (DL) component carrier (CC) and a uplink (UL)CC. The cell may be configured by downlink resources only, or may beconfigured by downlink resources and uplink resources. Since DLcoverage, which is a range within which the node is capable oftransmitting a valid signal, and UL coverage, which is a range withinwhich the node is capable of receiving the valid signal from the UE,depends upon a carrier carrying the signal, the coverage of the node maybe associated with coverage of the “cell” of radio resources used by thenode. Accordingly, the term “cell” may be used to represent servicecoverage of the node sometimes, radio resources at other times, or arange that signals using the radio resources can reach with validstrength at other times.

In carrier aggregation (CA), two or more CCs are aggregated. A UE maysimultaneously receive or transmit on one or multiple CCs depending onits capabilities. CA is supported for both contiguous and non-contiguousCCs. When CA is configured the UE only has one radio resource control(RRC) connection with the network. At RRC connectionestablishment/re-establishment/handover, one serving cell provides thenon-access stratum (NAS) mobility information, and at RRC connectionre-establishment/handover, one serving cell provides the security input.This cell is referred to as the Primary Cell (PCell). The PCell is acell, operating on the primary frequency, in which the UE eitherperforms the initial connection establishment procedure or initiates theconnection re-establishment procedure. Depending on UE capabilities,Secondary Cells (SCells) can be configured to form together with thePCell a set of serving cells. An SCell is a cell providing additionalradio resources on top of Special Cell. The configured set of servingcells for a UE therefore always consists of one PCell and one or moreSCells. For dual connectivity operation, the term Special Cell (SpCell)refers to the PCell of the master cell group (MCG) or the PSCell of thesecondary cell group (SCG). An SpCell supports PUCCH transmission andcontention-based random access, and is always activated. The MCG is agroup of serving cells associated with a master node, comprising of theSpCell (PCell) and optionally one or more SCells. The SCG is the subsetof serving cells associated with a secondary node, comprising of thePSCell and zero or more SCells, for a UE configured with dualconnectivity (DC). For a UE in RRC_CONNECTED not configured with CA/DCthere is only one serving cell comprising of the PCell. For a UE inRRC_CONNECTED configured with CA/DC the term “serving cells” is used todenote the set of cells comprising of the SpCell(s) and all SCells. InDC, two MAC entities are configured in a UE: one for the MCG and one forthe SCG.

FIG. 8 illustrates a data flow example in the 3GPP NR system.

In FIG. 8, “RB” denotes a radio bearer, and “H” denotes a header. Radiobearers are categorized into two groups: data radio bearers (DRB) foruser plane data and signalling radio bearers (SRB) for control planedata. The MAC PDU is transmitted/received using radio resources throughthe PHY layer to/from an external device. The MAC PDU arrives to the PHYlayer in the form of a transport block.

In the PHY layer, the uplink transport channels UL-SCH and RACH aremapped to their physical channels PUSCH and PRACH, respectively, and thedownlink transport channels DL-SCH, BCH and PCH are mapped to PDSCH,PBCH and PDSCH, respectively. In the PHY layer, uplink controlinformation (UCI) is mapped to PUCCH, and downlink control information(DCI) is mapped to PDCCH. A MAC PDU related to UL-SCH is transmitted bya UE via a PUSCH based on an UL grant, and a MAC PDU related to DL-SCHis transmitted by a BS via a PDSCH based on a DL assignment.

Data unit(s) (e.g. PDCP SDU, PDCP PDU, RLC SDU, RLC PDU, RLC SDU, MACSDU, MAC CE, MAC PDU) in the present disclosure is(are)transmitted/received on a physical channel (e.g. PDSCH, PUSCH) based onresource allocation (e.g. UL grant, DL assignment). In the presentdisclosure, uplink resource allocation is also referred to as uplinkgrant, and downlink resource allocation is also referred to as downlinkassignment. The resource allocation includes time domain resourceallocation and frequency domain resource allocation. In the presentdisclosure, an uplink grant is either received by the UE dynamically onPDCCH, in a Random Access Response, or configured to the UEsemi-persistently by RRC. In the present disclosure, downlink assignmentis either received by the UE dynamically on the PDCCH, or configured tothe UE semi-persistently by RRC signalling from the BS.

FIG. 9 shows an example of RRC reconfiguration procedure if the RRCreconfiguration is successful to which technical features of the presentdisclosure can be applied.

Referring to FIG. 9, in step S901, the network may transmit anRRCReconfiguration message to the UE. For example, a source RAN node maytransmit the RRCReconfiguration message comprising a mobility command ofa target RAN node for a mobility from the source RAN node to the targetRAN node.

In step S903, if RRC reconfiguration is successful, the UE may transmitan RRCReconfigurationComplete message to the network. TheRRCReconfigurationComplete message may comprise a mobility completemessage which informs that the UE successfully performed a mobility fromthe source RAN node to the target RAN node. For example, if the UEsuccessfully performed a mobility from the source RAN node to the targetRAN node—that is, if the UE successfully applied the mobility command ofthe target RAN node, the UE may transmit the mobility complete messageto the target RAN node.

FIG. 10 shows an example of RRC reconfiguration procedure if the RRCreconfiguration fails to which technical features of the presentdisclosure can be applied.

Referring to FIG. 10, in step S1001, the network may transmit anRRCReconfiguration message to the UE. For example, a source RAN node maytransmit the RRCReconfiguration message comprising a mobility command ofa target RAN node for a mobility from the source RAN node to the targetRAN node.

In step S1003, if RRC reconfiguration fails, the UE and the network mayperform RRC connection re-establishment. For example, if the UE fails toperform a mobility from the source RAN node to the target RAN node—thatis, if the UE fails to apply the mobility command of the target RANnode, the UE and the source RAN node may perform RRC connectionre-establishment.

The purpose of the RRC reconfiguration procedure as illustrated in FIGS.9 and 10 may be to modify an RRC connection, e.g. toestablish/modify/release RBs, to perform reconfiguration with sync, tosetup/modify/release measurements, to add/modify/release SCells and cellgroups. As part of the procedure, NAS dedicated information may betransferred from the Network to the UE.

In E-UTRAN-NR (EN)-dual connectivity (DC), SRB3 can be used formeasurement configuration and reporting, to (re-)configure MAC, RLC,physical layer and RLF timers and constants of the SCG configuration,and to reconfigure PDCP for DRBs associated with the S-KgNB or SRB3,provided that the (re-)configuration does not require any MeNBinvolvement.

The network may initiate the RRC reconfiguration procedure to the UE inRRC_CONNECTED. The network may apply the procedure as follows:

-   -   The establishment of RBs (other than SRB1, that is established        during RRC connection establishment) is performed only when AS        security has been activated;    -   The addition of Secondary Cell Group and SCells is performed        only when AS security has been activated;    -   The reconfigurationWithSync is included in secondaryCellGroup        only when at least one DRB is setup in SCG.

FIG. 11 shows an example of a dual connectivity (DC) architecture towhich technical features of the present disclosure can be applied. InFIG. 11 and throughout the disclosure, ‘radio access network (RAN) node’refers to a network entity to which a wireless device can access througha radio channel. Examples of the RAN node may comprise gNB, eNB, basestation, and/or cell.

Referring to FIG. 11, MN 1111, SN 1121, and a UE 1130 communicating withboth the MN 1111 and the SN 1121 are illustrated. As illustrated in FIG.11, DC refers to a scheme in which a UE (e.g., UE 1130) utilizes radioresources provided by at least two RAN nodes comprising a MN (e.g., MN1111) and one or more SNs (e.g., SN 1121). In other words, DC refers toa scheme in which a UE is connected to both the MN and the one or moreSNs, and communicates with both the MN and the one or more SNs. Sincethe MN and the SN may be in different sites, a backhaul between the MNand the SN may be construed as non-ideal backhaul (e.g., relativelylarge delay between nodes).

MN (e.g., MN 1111) refers to a main RAN node providing services to a UEin DC situation. SN (e.g., SN 1121) refers to an additional RAN nodeproviding services to the UE with the MN in the DC situation. If one RANnode provides services to a UE, the RAN node may be a MN. SN can existif MN exists.

For example, the MN may be associated with macro cell whose coverage isrelatively larger than that of a small cell. However, the MN does nothave to be associated with macro cell—that is, the MN may be associatedwith a small cell. Throughout the disclosure, a RAN node that isassociated with a macro cell may be referred to as ‘macro cell node’. MNmay comprise macro cell node.

For example, the SN may be associated with small cell (e.g., micro cell,pico cell, femto cell) whose coverage is relatively smaller than that ofa macro cell. However, the SN does not have to be associated with smallcell—that is, the SN may be associated with a macro cell. Throughout thedisclosure, a RAN node that is associated with a small cell may bereferred to as ‘small cell node’. SN may comprise small cell node.

The MN may be associated with a master cell group (MCG). MCG may referto a group of serving cells associated with the MN, and may comprise aprimary cell (PCell) and optionally one or more secondary cells(SCells). User plane data and/or control plane data may be transportedfrom a core network to the MN through a MCG bearer. MCG bearer refers toa bearer whose radio protocols are located in the MN to use MNresources. As shown in FIG. 11, the radio protocols of the MCG bearermay comprise PDCP, RLC, MAC and/or PHY.

The SN may be associated with a secondary cell group (SCG). SCG mayrefer to a group of serving cells associated with the SN, and maycomprise a primary secondary cell (PSCell) and optionally one or moreSCells. User plane data may be transported from a core network to the SNthrough a SCG bearer. SCG bearer refers to a bearer whose radioprotocols are located in the SN to use SN resources. As shown in FIG.11, the radio protocols of the SCG bearer may comprise PDCP, RLC, MACand PHY.

User plane data and/or control plane data may be transported from a corenetwork to the MN and split up/duplicated in the MN, and at least partof the split/duplicated data may be forwarded to the SN through a splitbearer. Split bearer refers to a bearer whose radio protocols arelocated in both the MN and the SN to use both MN resources and SNresources. As shown in FIG. 11, the radio protocols of the split bearerlocated in the MN may comprise PDCP, RLC, MAC and PHY. The radioprotocols of the split bearer located in the SN may comprise RLC, MACand PHY.

According to various embodiments, PDCP anchor/PDCP anchor point/PDCPanchor node refers to a RAN node comprising a PDCP entity which splitsup and/or duplicates data and forwards at least part of thesplit/duplicated data over X2/Xn interface to another RAN node. In theexample of FIG. 11, PDCP anchor node may be MN.

According to various embodiments, the MN for the UE may be changed. Thismay be referred to as handover, or a MN handover.

According to various embodiments, a SN may newly start providing radioresources to the UE, establishing a connection with the UE, and/orcommunicating with the UE (i.e., SN for the UE may be newly added). Thismay be referred to as a SN addition.

According to various embodiments, a SN for the UE may be changed whilethe MN for the UE is maintained. This may be referred to as a SN change.

According to various embodiments, DC may comprise E-UTRAN NR-DC (EN-DC),and/or multi-radio access technology (RAT)-DC (MR-DC). EN-DC refers to aDC situation in which a UE utilizes radio resources provided by E-UTRANnode and NR RAN node. MR-DC refers to a DC situation in which a UEutilizes radio resources provided by RAN nodes with different RATs.

FIG. 12 shows an example of a conditional handover procedure to whichtechnical features of the present disclosure can be applied. FIG. 12illustrates steps for the conditional handover procedure exemplary, butthe illustrated steps can also be applied to a conditional mobilityprocedure (e.g., conditional SN addition procedure and/or conditional SNchange procedure).

Referring to FIG. 12, in step S1201, the source cell may transmitmeasurement control message to the UE. The source cell may configure theUE measurement procedures according to the roaming and accessrestriction information and, for example, the available multiplefrequency band information through the measurement control message.Measurement control information provided by the source cell through themeasurement control message may assist the function controlling the UE'sconnection mobility. For example, the measurement control message maycomprise measurement configuration and/or report configuration.

In step S1203, the UE may transmit a measurement report message to thesource cell. The measurement report message may comprise a result ofmeasurement on neighbor cell(s) around the UE which can be detected bythe UE. The UE may generate the measurement report message according toa measurement configuration and/or measurement control information inthe measurement control message received in step S1201.

In step S1205, the source cell may make a handover (HO) decision basedon the measurement report. For example, the source cell may make a HOdecision and determine candidate target cells (e.g., target cell 1 andtarget cell 2) for HO among neighbor cells around the UE based on aresult of measurement (e.g., signal quality, reference signal receivedpower (RSRP), reference signal received quality (RSRP)) on the neighborcells.

In step S1207, the source cell may transmit HO request messages to thetarget cell 1 and the target cell 2 which are determined in step S1205.That is, the source cell may perform handover preparation with thetarget cell 1 and the target cell 2. The HO request message may comprisenecessary information to prepare the handover at the target side (e.g.,target cell 1 and target cell 2).

In step S1209, each of the target cell 1 and the target cell 2 mayperform an admission control based on information included in the HOrequest message. The target cell may configure and reserve the requiredresources (e.g., C-RNTI and/or RACH preamble). The AS-configuration tobe used in the target cell can either be specified independently (i.e.an “establishment”) or as a delta compared to the AS-configuration usedin the source cell (i.e. a “reconfiguration”).

In step S1211, the target cell and the target cell 2 may transmit a HOrequest acknowledge (ACK) message to the source cell. The HO request ACKmessage may comprise information on resources reserved and prepared fora handover. For example, the HO request ACK message may comprise atransparent container to be sent to the UE as an RRC message to performthe handover. The container may include a new C-RNTI, target gNBsecurity algorithm identifiers for the selected security algorithms, adedicated RACH preamble, and/or possibly some other parameters i.e.access parameters, SIBs. If RACH-less handover is configured, thecontainer may include timing adjustment indication and optionally apreallocated uplink grant. The HO request ACK message may also includeRNL/TNL information for forwarding tunnels, if necessary. As soon as thesource cell receives the HO request ACK message, or as soon as thetransmission of the handover command is initiated in the downlink, dataforwarding may be initiated.

In step S1213, the source cell may transmit a conditional HO (CHO)configuration to the UE. The CHO configuration may be also referred toas conditional reconfiguration. The CHO configuration may comprise a CHOconfiguration for each of the candidate target cells (e.g., target cell1, target cell 2). For example, the CHO configuration may comprise a CHOconfiguration for the target cell 1, and a CHO configuration for thetarget cell 2. The CHO configuration for the target cell 1 may comprisea handover condition for the target cell 1, and a handover command ofthe target cell 1. The handover command of the target cell 1 maycomprise RRC reconfiguration parameters for a handover to the targetcell 1, including information on resources reserved for the handover tothe target cell 1. Similarly, the CHO configuration for the target cell2 may comprise a handover condition for the target cell 2, and ahandover command of the target cell 2. The handover command of thetarget cell 2 may comprise RRC reconfiguration parameters for a handoverto the target cell 2, including information on resources reserved forthe handover to the target cell 2.

In step S1215, the UE may perform an evaluation of the handovercondition for the candidate target cells (e.g., target cell 1, targetcell 2) and select a target cell for handover among the candidate targetcells. For example, the UE may perform measurements on the candidatetarget cells, and determine whether a candidate target cell satisfies ahandover condition for the candidate target cell among the candidatetarget cells based on a result of the measurements on the candidatetarget cells. If the UE identifies that the target cell 1 satisfies ahandover condition for the target cell 1, the UE may select the targetcell 1 as a target cell for the handover.

In step S1217, the UE may perform a random access to the selected targetcell (e.g., target cell 1). For example, the UE may transmit a randomaccess preamble to the target cell 1, and receive a random accessresponse comprising an uplink grant from the target cell 1. If RACH-lesshandover is configured, the step S1217 may be omitted, and the uplinkgrant may be provided in step S1213.

In step S1219, the UE may transmit a HO complete message to the targetcell 1. When the UE has successfully accessed the target cell 1 (or,received uplink grant when RACH-less HO is configured), the UE maytransmit a HO complete message comprising a C-RNTI to confirm thehandover, along with uplink buffer status report, whenever possible, tothe target cell 1 to indicate that the handover procedure is completedfor the UE. The target cell 1 may verify the C-RNTI transmitted in theHO complete message.

In step S1221, the target cell 1 may transmit a sequence number (SN)status request message to the source cell. The target cell 1 may requestthe source cell to inform the target cell 1 of a SN of a packet thetarget cell 1 has to transmit after the handover, via the SN statusrequest message.

In step S1223, the source cell may transmit a CHO cancellation messageto the target cell 2 which is not selected as a target cell for ahandover among the candidate target cells. After receiving the CHOcancellation message, the target cell 2 may release resources that arereserved in case of a handover.

In step S1225, the target cell 2 may transmit a CHO cancellationconfirmation message to the source cell, as a response for the CHOcancellation message. The CHO cancellation confirmation message mayinform that the target cell 2 has released resources reserved in case ofa handover.

In step S1227, the source cell may transmit a SN status transfer messageto the target cell 1, as a response for the SN status request message.The SN status transfer message may inform the target cell 1 of a SN of apacket the target cell 1 has to transmit after the handover.

In step S1229, the source cell may perform a data forwarding to thetarget cell 1. For example, the source cell may forward data receivedfrom a core network to the target cell 1 so that the target cell 1 cannow transmit the data to the UE.

For conditional handover, UE may report many cells or beams as thepossible candidate HO targets based on the radio resource management(RRM) measurement. gNB may issue the conditional handover commands forone or multiple candidate target cells reported by the UE. Within theCHO configuration, the candidate target cells may be configured withdifferent HO conditions (e.g., event, TTT, offset value, to-be-measuredRS and/or threshold) and possibly uplink access resources for UE access(e.g. random access preambles).

As illustrated in FIG. 12, when the UE receives a CHO configuration(including a handover command for the conditional handover), the UE maystart evaluating the handover condition for CHO while continuing tooperate based on current RRC configuration of the UE. When the UEdetermines that the HO condition for conditional HO is fulfilled, the UEmay disconnect from the source cell, and apply the CHO configuration andaccess to the target cell.

From the network side, the base station related to the source cell mayneed to prepare the handover with one or multiple target cells. Forexample, the source cell may need to request the candidate targetcell(s) to perform admission control and reserve the radio resourcesaccordingly. There may be multiple options (on the exact time point) forthe source cell to stop data transmission to the UE, and to start dataforwarding to the candidate target cells. The source cell will know theexact target cell for the UE after the target cell indicates to thesource cell that it is selected as the exact target cell when thehandover procedure is successfully executed.

CHO is essentially a network-configured but UE-controlled downlinkmobility mechanism with a potential to reduce the interruption time andhandover failure (HOF)/radio link failure (RLF).

The HO condition may not be fulfilled for a long time period and hencethe UE will stay in the source cell. In this case, the source cell musthave the possibility to perform further reconfigurations either tochange the UE operation in the current source cell or to command the UEto handover to a suitable target cell.

If conditional handover is configured, UE may receive multiple handovercommands for multiple target cells, and will finally select a singletarget cell to perform handover.

According to conditional handover procedure as illustrated in FIG. 12,one or more RRC reconfiguration messages to be transmitted to the UE mayinclude multiple handover commands. Thus, signaling overhead may beexpected to be significant for support of conditional handover.

In the conditional handover procedure, UE may receive a firstconfiguration from a source cell and then receive handover commandincluding a second configuration from the target cell. Upon receivingthe second configuration after applying the first configuration with aconfigured parameter value, if the configured parameter value is absentin the second configuration, UE maintains the configured parameter valueof the first configuration after applying the second configuration i.e.after completing handover to the target cell.

Various embodiments of the present disclosure can be applied toconditional mobility, in which one or more candidate cells aredetermined based on a mobility condition first, and actual mobility isperformed towards one of the candidate cells. The conditional mobilitymay include conditional handover, conditional SCG change, and/orconditional SCG addition. The mobility command may be a message used for‘reconfiguration with sync’.

FIG. 13 shows an example of a method for mobility management accordingto an embodiment of the present disclosure. The steps illustrated inFIG. 13 may be performed by a wireless device and/or UE.

Referring to FIG. 13, in step S1301, the wireless device may receive afirst message comprising mobility commands of candidate target cells.Each of the mobility commands may be related to an index. The index mayalso be referred to as configuration identity. The first message may bea conditional reconfiguration message or CHO configuration message.Throughout the disclosure, the candidate target cell can be simplyreferred to as target cell.

In step S1303, the wireless device may receive a second messagecomprising the index related to a first mobility command of a candidatetarget cell among the mobility commands, and a second mobility commandof the candidate target cell. The second message may be received afterthe first message is received. The first mobility command may compriseRRC reconfiguration parameters for a mobility to the candidate targetcell, and the second mobility command may comprise one or more updatedRRC reconfiguration parameters for a mobility to the candidate targetcell. For example, the second mobility command may include parametervalues of at least one first entry that are updated from those (or,different from) of the at least one first entry in the first mobilitycommand, and exclude parameter values of at least one second entry thatare included in the first mobility command. That is, the parametervalues of the at least one second entry in the first mobility commandmay not be included in the second mobility command.

In step S1305, the wireless device may update the first mobility commandbased on the second mobility command. For example, the wireless devicemay identify, in the first mobility command, the parameter values of theat least one second entry that are excluded in the second mobilitycommand. Then, the wireless device may add the parameter values of theat least one second entry to the second mobility command to obtain anupdated version of the first mobility command. For another example, thewireless device may replace the parameter values of the at least onefirst entry in the first mobility command with those of the at least onefirst entry in the second mobility command to obtain an updated versionof the first mobility command. Herein, the updated version of the firstmobility command may also be referred to as updated first mobilitycommand. Therefore, the updated first mobility command may compriseparameter values of at least one first entry included in the secondmobility command, and parameter values of at least one second entryincluded in the first mobility command.

According to various embodiments, the first message may comprise atleast one of a mobility command of each of the candidate target cells,an index related to the mobility command, or a mobility condition foreach of the candidate target cells. For example, the first message maycomprise at least one of the first mobility command of the candidatetarget cell, the index related to the first mobility command, or amobility condition for the candidate target cell. The mobility conditionmay be a triggering condition for a mobility to a target cell.

According to various embodiments, the index related to a mobilitycommand may comprise an index of a candidate target cell related to themobility command.

According to various embodiments, the wireless device may store themobility commands in the first message. The wireless device mayidentify, among the stored mobility commands, the first mobility commandrelated to the index included in the second message. The wireless devicemay update the identified first mobility command based on the secondmobility command included in the second message.

According to various embodiments, the wireless device may, uponidentifying that the candidate target cell satisfies a mobilitycondition for the candidate target cell, perform a mobility to thecandidate target cell based on the updated first mobility command. Thewireless device may determine whether the candidate target cellsatisfies a mobility condition for the candidate target cell or does notsatisfy the mobility condition for the candidate target cell based on aresult of a measurement on the candidate target cell (e.g., signalquality, RSRP, RSRQ).

According to various embodiments, the wireless device may, uponidentifying that the candidate target cell satisfies a handovercondition for the candidate target cell, perform a handover to thecandidate target cell based on the updated first mobility command (i.e.,updated handover command).

According to various embodiments, the wireless device may be incommunication with a MN and a SN in DC. The wireless device may, uponidentifying that the candidate target cell satisfies a SN changecondition for the candidate target cell, perform a SN change from the SNto another SN related to the candidate target cell based on the updatedfirst mobility command (i.e., updated SN change command).

According to various embodiments, the wireless device may, uponidentifying that the candidate target cell satisfies a SN additioncondition for the candidate target cell, perform a SN addition for a RANnode related to the candidate target cell based on the updated firstmobility command (i.e., updated SN addition command). That is, thewireless device may perform a procedure for adding the RAN node relatedto the candidate target cell as a SN for the wireless device. Thisprocedure causes a RAN node related to a source cell to become a MN, andthe wireless device to be in communication with the MN and the SN in DC.

According to various embodiment, the wireless device may identify, amongindexes related to the mobility commands, one or more indexes for whichmobility conditions are satisfied. Throughout the disclosure, ifmobility condition for a candidate target cell is satisfied, an indexrelated to a mobility command of the target cell may be referred to as‘an index for which mobility condition is satisfied’. The wirelessdevice may identify, among the candidate target cells, one or morecandidate target cells related to one or more mobility commands havingthe one or more indexes. The wireless device may select a target cellamong the one or more candidate target cells for a mobility.

According to various embodiments, the wireless device may identify amobility command of the target cell. The mobility command of the targetcell may comprise a handover command of the selected target cell. Thewireless device may apply parameter values in the handover command ofthe target cell to perform a handover to the target cell.

According to various embodiments, the wireless device may be incommunication with a MN and a SN in a DC. The wireless device mayidentify a mobility command of the target cell. The mobility command ofthe target cell may comprise a SN change command of the target cell. Thewireless device may apply parameter values in the SN change command ofthe target cell to perform a SN change from the SN to another SN relatedto the target cell.

According to various embodiments, the wireless device may identify amobility command of the target cell. The mobility command of the targetcell may comprise a SN addition command of the target cell. The wirelessdevice may apply parameter values in the SN addition command of thetarget cell to perform a SN addition for a RAN node related to thetarget cell.

FIG. 14 shows an example of a method to perform a mobility to a targetcell according to an embodiment of the present disclosure. The stepsillustrated in FIG. 14 may be performed by a wireless device and/or aUE.

Referring to FIG. 14, in step S1401, the UE may receive and store firstmobility commands. While connected to a source cell, the UE may receiveand store more than one first mobility commands from a source cell.Different mobility commands may be used for mobility to different firsttarget cells. The first target cells may be cells which the UE mayfinally configure as serving cells. Different mobility commands may beidentified by different indexes (e.g., target cell ID). The UE may alsoreceive the indexes related to the first mobility commands together withthe first mobility commands from the source cell.

In step S1403, the UE may receive a second mobility command indicatingone of the indexes previously received from the source cell. Whileconnected to the source cell, UE may receive a second mobility commandindicating one of the indexes previously received from the source cell.The second mobility command may be used for mobility to the secondtarget cell. The second target cell may be one of the first target cellsor a target cell other than the first target cells which UE may finallyconfigure as a serving cell. The second mobility command may beassociated with a mobility condition for mobility to the second targetcell.

In step S1405, the UE may update the first mobility command based on thesecond mobility command. If a particular parameter value included in afirst mobility command identified by the indicated index among the firstmobility commands is absent in the second mobility command, UE may addthe particular parameter value to the second mobility command to obtainthe updated first mobility command. That is, the UE may replaceparameter values included in the first mobility command with thoseincluded in the second mobility command to obtain the updated firstmobility command. The first mobility command may be associated with avalidity time. UE may start a timer upon receiving the first mobilitycommand. If the timer reaches the validity time, the timer expires andso UE may invalidate the first mobility command. If the first mobilitycommand is valid based on the validity time (i.e., the timer has notreached the validity time and/or the timer has not expired), UE may addthe particular parameter value to the second mobility command. If thefirst mobility command is invalid based on the validity time (i.e., thetimer has reached the validity time and/or the timer has expired), UEmay apply the second mobility command without adding the particularparameter to the second mobility command or may discard the secondmobility command. The UE may remove association between the indicatedindex and the first mobility command, and then consider that theindicated index is reused for the second mobility command after storingthe second mobility command. Alternatively, if a new index is receivedfor the second mobility command in addition to the index related to thefirst mobility command, UE may keep storing the first mobility commandin association with the indicated index and store the second mobilitycommand in associated with the new index.

In step S1407, the UE may apply the second mobility command and thenperform RACH transmission towards a target cell. If mobility conditionfor the second target cell is met for mobility to the second targetcell, UE may apply the second mobility command with the added parametervalue and then perform RACH transmission (i.e., random access preamble)towards the second target cell for mobility. Then, the UE may receive anuplink grant as a response, and transmit a mobility complete message tothe second target cell based on the uplink grant if the UE successfullyperformed a mobility to the second target cell. If RACH-less mobility isconfigured, the UE may not perform the RAH transmission. Instead, the UEmay transmit a mobility complete message to the second target cell basedon an uplink grant previously received before, if the UE successfullyperformed a mobility to the second target cell.

In step S1409, the UE may remove the stored first mobility commandsafter completing mobility to the target cell (e.g., after transmittingthe mobility complete message to the second target cell).

FIG. 15 shows an example of a method for performing a mobility to atarget cell according to an embodiment of the present disclosure. Thesteps illustrated in FIG. 15 may be performed by a source RAN node (or,source gNB, source eNB, source base station, source cell).

Referring to FIG. 15, in step S1501, the source RAN node may establish aconnection with a UE at a source cell.

In step S1503, the source RAN node may receive one or more firstmobility commands from one or more target RAN nodes. The source RAN nodemay request the first mobility commands to the target RAN nodes viamobility request messages and then the target RAN nodes may provide thefirst mobility commands to the source RAN node via mobility request ACKmessages. Different first mobility commands may be identified bydifferent indexes. The index value may be set by the source RAN node orthe target RAN nodes. The index may be associated with a cell of thetarget RAN nodes and may be the identity of the associated cell of thetarget RAN nodes.

In step S1505, the source RAN node may provide the UE with the one ormore first mobility commands. Different first mobility commands may beidentified by different indexes. Different mobility commands may be usedfor UE's mobility to different first target cells. Different firstmobility commands may be contained in different containers of a RRCmessage (e.g., conditional reconfiguration message or CHO configurationmessage) delivered to the UE. The first mobility command may beassociated with a mobility condition for UE's mobility to a target cell.The source RAN node may provide the UE with the mobility condition aswell as the first mobility command.

In step S1507, the source RAN node may construct a second mobilitycommand for updating one of the one or more first mobility commands. Thesource RAN node or one of the target RAN nodes may choose one of thefirst mobility commands and the construct a second mobility command inwhich a particular parameter value included in the chosen first mobilitycommand is absent. The index identifying the chosen first mobilitycommand or a new index may be used to identify the second mobilitycommand. The absent particular parameter value may be implicitlyincluded in the second mobility command. If one of the target RAN nodesconstruct the second mobility command, the source gNB may receive thesecond mobility commands from the target RAN node. The second mobilitycommand may be used for UE's mobility to the second target cell. Thesecond mobility command may be associated with a mobility condition formobility to the second target cell. If the mobility condition is met formobility to the second target cell, UE may apply the second mobilitycommand with the added parameter value and then perform RACHtransmission towards the second target cell for mobility. However, ifRACH-less mobility is configured, the UE may not perform the RACHtransmission. The first mobility command may be associated with avalidity time. UE may start a timer upon receiving the first mobilitycommand. If the timer reaches the validity time, the timer expires andso UE may invalidate the first mobility command. The particularparameter value can be absent only if the first mobility command isvalid based on the validity time (i.e., the timer has not reached thevalidity time and/or the timer has not expired).

In step S1509, the source RAN node may transmit, to the UE, the secondmobility command and an index of the first mobility command to update.The source RAN node may transmit the second mobility command to the UEwith the index that was previously received by the UE. The secondmobility command may be used for mobility to the second target cell. Thesecond mobility command may be associated with a mobility condition formobility to the second target cell. The source RAN node may provide theUE with the mobility condition as well as the second mobility command.The second mobility command may be associated with a target cell of thetarget RAN nodes. If a particular parameter value included in the firstmobility command identified by the indicated index is absent in thesecond mobility command, UE may add the particular parameter value tothe second mobility command to obtain the updated first mobilitycommand. That is, the UE may replace parameter values included in thefirst mobility command with those included in the second mobilitycommand to obtain the updated first mobility command.

After step S1509, if the target RAN node receives an uplink message(i.e., mobility complete message) from the UE at a target cellassociated with the index and the second mobility command, the targetRAN node may consider mobility to be successfully completed for the UE.The target RAN node may apply the second mobility command to the UE. Theuplink message (i.e., mobility complete message) may be transmitted viaRACH procedure initiated by the UE. If RACH-less mobility is configured,the UE may not perform the RAH transmission. Instead, the UE maytransmit a mobility complete message to the second target cell based onan uplink grant previously received before, if the UE successfullyperformed a mobility to the second target cell.

FIG. 16 shows an example of signal flows for updating a mobility commandin a mobility procedure according to an embodiment of the presentdisclosure. FIG. 16 illustrates steps for the conditional handoverprocedure exemplary, but the illustrated steps can also be applied to aconditional mobility procedure (e.g., conditional SN addition procedureand/or conditional SN change procedure). The steps performed by UE inFIG. 16 can also be performed by a wireless device.

Referring to FIG. 16, in step S1601, while the UE is connected to asource cell of a source RAN node, the UE may receive a measurementcontrol message comprising a measurement configuration from the sourceRAN node. That is, measurement may be configured by the source RAN nodevia the measurement control message. The UE may perform measurementbased on the measurement configuration.

In step S1603, if a measurement report is triggered, the UE may send themeasurement report to the source RAN node.

In step S1605, the source RAN node may make a HO decision based on themeasurement report. That is, based on the measurement report or so, thesource RAN node may select one or more target cells (e.g., target cell 1and target cell 2) of one or more target gNBs for conditional handover.

In step S1607, the source RAN node may transmit HO request messages tothe target cell 1 and the target cell 2. The source RAN node may requestconditional handover to the target RAN nodes via the HO requestmessages.

In step S1609, each of the target cell 1 and the target cell 2 mayperform an admission control based on information included in the HOrequest message. The target cell may configure and reserve the requiredresources (e.g., C-RNTI and/or RACH preamble).

In step S1611, the target RAN nodes may provide their handover commands(i.e., handover command 1 of the target cell 1, and handover command 2of the target cell 2) to the source RAN node via HO request ACKmessages. The first handover commands (i.e., HO command 1 and HO command2) may be identified by different indexes. For example, HO command 1 maybe identified by index 1, and HO command 2 may be identified by index 2.The index value may be set by the source RAN node or the target RANnodes. The index may be associated with the target cell of the targetgNBs. For example, the index may be the identity of the associated cellof the target gNBs. The source RAN node may receive two handovercommands from the target RAN nodes. Different handover commands, (i.e.HO command 1 & 2) may be used for handover to different target cells(i.e. target cell 1 & 2). For example, HO command 1 may be used forhandover to target cell 1, and HO command 2 may be used for handover totarget cell 2. Different handover commands may be identified bydifferent indexes.

In step S1613, the source RAN node may construct a RRC message (e.g.,conditional reconfiguration message or CHO configuration message)containing two handover commands received from the target RAN nodes, andthen transmit the RRC message to the UE. While connected to the sourcecell, UE may receive the RRC message including the handover commands.Each handover command may indicate/be related to an index and a handovercondition.

In step S1615, the UE may store the received handover commands withtheir indexes and handover conditions.

At least one of the target RAN nodes may update its handover command.Alternatively, the source RAN node may update one of the handovercommands. For updating the handover command, the source RAN node or thetarget RAN nodes may choose the handover command previously transmittedto the UE, and then construct an updated handover command in which aparticular parameter value included in the chosen handover command isabsent. If one of the target RAN nodes (e.g., target cell 1) updates thehandover command, in step S1617, the target RAN node (e.g., targetcell 1) may provide the updated handover command (e.g., delta for HOcommand 1) to the source RAN node with an index (e.g., index 1) relatedto the handover command.

In step S1619, the source RAN node may transmit the updated handovercommand to the UE with the index associated with the chosen previoushandover command. The updated handover command may be used for handoverto the target cell 1. The updated handover command may be associatedwith a mobility condition for handover to the target cell 1. Whileconnected to the source cell, UE may receive the updated handovercommand for the target cell 1.

In step S1621, UE may update HO command 1. If a particular parametervalue included in the previous handover command identified by theindicated index is absent in the updated handover command, UE may addthe particular parameter value to the updated handover command. That is,the UE may replace parameter values included in the previous handovercommand with those included in the updated handover command. Thehandover command may be associated with a validity time. UE may start atimer upon receiving a handover command. If the timer reaches thevalidity time, the timer expires and so UE may invalidate the handovercommand. If the handover command is valid based on the validity time(i.e., the timer has not reached the validity time and/or the timer hasnot expired) and an updated handover command is received, UE may add theparticular parameter value to the updated handover command. If thehandover command is invalid based on the validity time (i.e., the timerhas reached the validity time and/or the timer has expired), UE mayapply the updated handover command without the particular parameter ordiscards the updated handover command.

To identify the updated handover command, the index identifying theprevious handover command or a new index may be used. For example, UEmay remove association between the indicated index and the previoushandover command from UE's storage. Then, UE may consider the indicatedindex is reused for the updated handover command after storing theupdated handover command. Alternatively, if a new index is receivedtogether with the updated handover command in addition to the indexrelated to the previous handover command, UE may keep storing theprevious handover command in association with the indicated index whilestoring the updated handover command in association with the new indexfor the target cell 1.

In step S1623, the UE may evaluate handover condition for target cellsand select a target cell for handover. For example, the UE may performmeasurements on two target cells (e.g., target cell 1 and target cell2). Based on a result of the measurements, the UE may identify that thehandover condition is met for handover to the target cell 1.

In step S1625, the UE may apply the handover command stored for thetarget cell 1 with the added parameter value. Then, UE may synchronizeto downlink of the target cell 1.

In step S1627, the UE may perform RACH transmission towards the targetcell 1. In a random access procedure, the UE may receive an uplinkgrant. If RACH-less handover is configured, the step S1627 may beomitted, and the uplink grant may be provided in advance.

In step S1629, the UE may transmit a MAC PDU containing a handovercomplete message to the target cell 1 based on the uplink grant. Aftersuccessfully completing handover, the UE may remove the handovercommands stored for the other target cell (e.g., target cell 2) fromUE's storage.

So far, conditional mobility (i.e., conditional handover, conditional SNchange and/or conditional SN addition) is described. Conditionalmobility is a kind of conditional reconfiguration. Herein after,Conditional reconfiguration is described.

The network may configure the UE with conditional reconfiguration (i.e.,conditional handover and/or conditional PSCell addition/change)including per candidate target cell an RRCConnectionReconfiguration(i.e., conditional mobility command) to only be applied upon thefulfillment of an associated execution condition (i.e., mobilitycondition).

For conditional reconfiguration, the UE shall:

1> if the received conditionalReconfiguration includes thecondReconfigurationToRemoveList:

2> perform the conditional reconfiguration removal procedure;

1> if the received conditionalReconfiguration includes thecondReconfigurationToAddModList:

2> perform the conditional reconfiguration addition/modificationprocedure.

I. Conditional Reconfiguration Addition/Modification

The UE shall:

1> for each condReconfigurationId (i.e., index related to a mobilitycommand) included in the received condReconfigurationToAddModList:

2> if an entry with the matching condReconfigurationId exists in thecondReconfigurationList within the VarConditionalReconfiguration (i.e.,list of {index, mobility condition, mobility command} for each targetcell stored in the UE):

3> replace the entry with the values received for thiscondReconfigurationId;

2> else:

3> add a new entry for this condReconfigurationId within theVarConditionalReconfiguration;

3> store the associated RRCConnectionReconfiguration (i.e., mobilitycommand and/or mobility condition) in VarConditionalReconfiguration;

2> monitor the triggering conditions (i.e., mobility conditions)associated to the measurement identities of that condReconfigurationId;

II. Conditional Reconfiguration Removal

The UE shall:

1> for each condReconfigurationId included in the receivedcondReconfigurationToRemoveList that is part of the current UEconfiguration in VarConditionalReconfiguration:

2> stop the monitoring of triggering conditions linked by themeasurement identities;

2> remove the entry with the matching condReconfigurationId from thecondReconfigurationList within the VarConditionalReconfiguration; The UEdoes not consider the conditional reconfiguration message as erroneousif the condReconfigurationToRemoveList includes anycondReconfigurationId value that is not part of the current UEconfiguration.

III. Conditional Reconfiguration Execution

For the measId for which the triggering condition for conditionalreconfiguration was fulfilled, the UE shall:

1> for each condReconfigurationId within theVarConditionalReconfiguration that has that measId associated to itsstored RRCConnectionReconfiguration (i.e., mobility command):

2> if all triggering conditions are fulfilled for thatcondReconfigurationId:

3> consider the target cell candidate within the storedRRCConnectionReconfiguration, associated to that condReconfigurationId,as a triggered cell;

1> if the more than one triggered cell exists:

2> select one of the triggered cells as the selected cell forconditional reconfiguration;

1> for the selected cell of conditional reconfiguration:

2> if the stored RRCConnectionReconfiguration associated to the selectedcell includes mobilityControlInfo (conditional handover):

3> apply the stored RRCConnectionReconfiguration associated to thatcondReconfigurationId and perform a handover to the selected cell;

2> else if the stored RRCConnectionReconfiguration includes nr-Config(conditional PSCell addition/change):

3> apply the stored RRCConnectionReconfiguration associated to thatcondReconfigurationId and perform the SN change/addition procedure forthe selected cell;

If multiple cells are triggered in conditional PSCell addition/changeexecution, the UE may consider beams and beam quality to select one ofthe triggered cells for execution.

The structure of the conditional reconfiguration message or theinformation element (IE) ConditionalReconfiguration may be as thefollowing Table 5. The IE ConditionalReconfiguration may be used to add,modify or release the configuration of a conditional handover, aconditional PSCell addition/change per target candidate cell.

TABLE 5 -- ASN1START ConditionalReconfiguration-r16 ::= SEQUENCE {condReconfigurationToAddModList-r16 CondReconfigurationToAddModList-r16OPTIONAL, -- Need ON condReconfigurationToRemoveList-r16 CondReconfigurationToRemoveList-r16 OPTIONAL, -- Need ON ... }CondReconfigurationToRemoveList-r16 ::= SEQUENCE (SIZE(1..maxCondConfig-r16)) OF CondReconfigurationId-r16 -- ASN1STOP

In Table 5, condReconfigurationToAddModList may refer to list ofconditional reconfigurations (i.e. conditional handover or conditionalPSCell change/addition) to add and/or modify. Also,condReconfigurationToRemoveList may refer to list of conditionalreconfigurations (i.e. conditional handover or conditional PSCellchange/addition) to remove. CondReconfigurationId may refer to an indexrelated to a mobility command.

The contents of the IE CondReconfigurationId may be as the followingTable 6. The IE ConditionalReconfigurationId may be used to identify aconditional reconfiguration.

TABLE 6 -- ASN1START CondReconfigurationId-r16 ::= INTEGER (1..maxCondConfig-r16) -- ASN1STOP

In Table 6, maxCondConfig may refer to the maximum number of conditionalreconfigurations (i.e., CondReconfigurationAddMods).

The structure of IE CondReconfigurationToAddModList may be as thefollowing Table 7. The IE CondReconfigurationToAddModList may concern alist of conditional reconfigurations (i.e. conditional handover,conditional PSCell addition/change) to add or modify, with for eachentry the measId (associated to the triggering condition configuration)and the associated RRCConnectionReconfiguration.

TABLE 7 -- ASN1START CondReconfigurationToAddModList-r16 ::= SEQUENCE(SIZE (1.. maxCondConfig-r16)) OF CondReconfigurationAddMod-r16CondReconfigurationAddMod-r16 ::= SEQUENCE { condReconfigurationId-r16CondReconfigurationId-r16, triggerCondition-r16 SEQUENCE (SIZE (1..2))OF MeasId, condReconfigurationToApply-r16 OCTET STRING (CONTAININGRRCConnectionReconfiguration), ... } -- ASN1STOP

In Table 7, CondReconfigurationAddMod may refer to a conditionalreconfiguration for a target cell. CondReconfigurationId may refer to anindex of the CondReconfigurationAddMod, which may be related to amobility command of the target cell. The triggerCondition may refer to amobility condition for the target cell. The RRCConnectionReconfigurationcontained in the condReconfigurationToApply may refer to a mobilitycommand of the target cell.

As described above, the conditional reconfiguration may also be referredto as CHO configuration. The structure of the CHO configuration or IECHOConfiguration may be as the following Table 8:

TABLE 8 CHOConfiguration ::= SEQUENCE { choToReleaseList-r16CHOToReleaseList-r16 OPTIONAL, -- Need N choToAddModList-r16CHOToAddModList-r16 OPTIONAL  -- Need N choConditionListSEQUENCE (SIZE (1..maxFFS)) OF CHOCondition-r16  OPTIONAL }CHOToReleaseList-r16 ::= SEQUENCE (SIZE (1..maxCHO)) OF CHOToRelease-r16 CHOToRelease-r16 ::= SEQUENCE { choId-r16 INTEGER (1..maxCHO) }CHOToAddModList-r16 ::= SEQUENCE (SIZE (1..maxCHO)) OF CHOToAddMod- r16CHOToAddMod-r16 ::= SEQUENCE { choId-r16 INTEGER (1..maxCHO),conditionId-r16 ReportConfigId OPTIONAL, -- Need MchoCellConfiguration-r16 OCTET STRING (CONTAINING FFS forCHOCellConfiguration-r16) OPTIONAL, -- Need M }

In Table 8, CHOToReleaseList may correspond tocondReconfigurationToRemoveList. CHOToAddModList may correspond toCondReconfigurationToAddModList. CHOCondition may correspond totriggerCondition. The maxCHO may correspond to maxCondConfig. That is,the maxCHO may refer to the maximum number of CHO configurations (i.e.,CHOToAddMods). The choId may correspond to condReconfigurationId.CHOToAddMod may correspond to CondReconfigurationToAddMod, which mayrefer to a CHO configuration for a target cell. The choId may refer toan index of the CondReconfigurationToAddMod, which may be related to amobility command of the target cell. The conditionId may refer to anindex of the CHOCondition (i.e., mobility condition for the targetcell), which may be related to a choConditionConfig. TheCHOCellConfiguration contained in the choCellConfiguration may refer toa mobility command of the target cell. The choCellConfiguration maycorrespond to condReconfigurationToApply.

The structure of IE CHOCondition may be as the following Table 9:

TABLE 9 -- ASN1START -- TAG-CHOTRIGGERCONDITION-STARTCHOCondition-r16-IEs ::= SEQUENCE { conditionId-r16 ReportConfigIdchoConditionConfig CHOConditionConfig-r16 OPTIONAL -- Cond NewID }CHOConditionConfig-r16-IE ::= SEQUENCE { eventId CHOICE { eventA3SEQUENCE { a3-Offset MeasTriggerQuantityOffset, hysteresis  Hysteresis,timeToTrigger TimeToTrigger, }, eventA5 SEQUENCE{ a5-Threshold1MeasTriggerQuantity, a5-Threshold2 MeasTriggerQuantity, hysteresis Hysteresis, timeToTrigger TimeToTrigger, }, ... }, rsType NR-RS-Type, ... } -- TAG-CHOTRIGGERCONDITION-STOP -- ASN1STOP

FIG. 17 shows a UE to implement an embodiment of the present disclosure.The present disclosure described above for UE side may be applied tothis embodiment.

A UE includes a processor 1710, a power management module 1711, abattery 1712, a display 1713, a keypad 1714, a subscriber identificationmodule (SIM) card 1715, a memory 1720, a transceiver 1730, one or moreantennas 1731, a speaker 1740, and a microphone 1741.

The processor 1710 may be configured to implement proposed functions,procedures and/or methods described in this description. Layers of theradio interface protocol may be implemented in the processor 1710. Theprocessor 1710 may include application-specific integrated circuit(ASIC), other chipset, logic circuit and/or data processing device. Theprocessor 1710 may be an application processor (AP). The processor 1710may include at least one of a digital signal processor (DSP), a centralprocessing unit (CPU), a graphics processing unit (GPU), a modem(modulator and demodulator). An example of the processor 1710 may befound in SNAPDRAGON series of processors made by Qualcomm®, EXYNOS™series of processors made by Samsung®, A series of processors made byApple®, HELIO™ series of processors made by MediaTek®, ATOM™ series ofprocessors made by Intel® or a corresponding next generation processor.

The processor 1710 may be configured to, or configured to control thetransceiver 1730 to implement steps performed by the UE and/or thewireless device throughout the disclosure.

The power management module 1711 manages power for the processor 1710and/or the transceiver 1730. The battery 1712 supplies power to thepower management module 1711. The display 1713 outputs results processedby the processor 1710. The keypad 1714 receives inputs to be used by theprocessor 1710. The keypad 1714 may be shown on the display 1713. TheSIM card 1715 is an integrated circuit that is intended to securelystore the international mobile subscriber identity (IMSI) number and itsrelated key, which are used to identify and authenticate subscribers onmobile telephony devices (such as mobile phones and computers). It isalso possible to store contact information on many SIM cards.

The memory 1720 is operatively coupled with the processor 1710 andstores a variety of information to operate the processor 1710. Thememory 1720 may include read-only memory (ROM), random access memory(RAM), flash memory, memory card, storage medium and/or other storagedevice. When the embodiments are implemented in software, the techniquesdescribed herein can be implemented with modules (e.g., procedures,functions, and so on) that perform the functions described herein. Themodules can be stored in the memory 1720 and executed by the processor1710. The memory 1720 can be implemented within the processor 1710 orexternal to the processor 1710 in which case those can becommunicatively coupled to the processor 1710 via various means as isknown in the art.

The transceiver 1730 is operatively coupled with the processor 1710, andtransmits and/or receives a radio signal. The transceiver 1730 includesa transmitter and a receiver. The transceiver 1730 may include basebandcircuitry to process radio frequency signals. The transceiver 1730controls the one or more antennas 1731 to transmit and/or receive aradio signal.

The speaker 1740 outputs sound-related results processed by theprocessor 1710. The microphone 1741 receives sound-related inputs to beused by the processor 1710.

FIG. 18 shows another example of a wireless communication system towhich the technical features of the present disclosure can be applied.

Referring to FIG. 18, the wireless communication system may include afirst device 1810 (i.e., first device 210) and a second device 1820(i.e., second device 220).

The first device 1810 may include at least one transceiver, such as atransceiver 1811, and at least one processing chip, such as a processingchip 1812. The processing chip 1812 may include at least one processor,such a processor 1813, and at least one memory, such as a memory 1814.The memory may be operably connectable to the processor 1813. The memory1814 may store various types of information and/or instructions. Thememory 1814 may store a software code 1815 which implements instructionsthat, when executed by the processor 1813, perform operations of thefirst device 910 described throughout the disclosure. For example, thesoftware code 1815 may implement instructions that, when executed by theprocessor 1813, perform the functions, procedures, and/or methods of thefirst device 1810 described throughout the disclosure. For example, thesoftware code 1815 may control the processor 1813 to perform one or moreprotocols. For example, the software code 1815 may control the processor1813 to perform one or more layers of the radio interface protocol.

The second device 1820 may include at least one transceiver, such as atransceiver 1821, and at least one processing chip, such as a processingchip 1822. The processing chip 1822 may include at least one processor,such a processor 1823, and at least one memory, such as a memory 1824.The memory may be operably connectable to the processor 1823. The memory1824 may store various types of information and/or instructions. Thememory 1824 may store a software code 1825 which implements instructionsthat, when executed by the processor 1823, perform operations of thesecond device 1820 described throughout the disclosure. For example, thesoftware code 1825 may implement instructions that, when executed by theprocessor 1823, perform the functions, procedures, and/or methods of thesecond device 1820 described throughout the disclosure. For example, thesoftware code 1825 may control the processor 1823 to perform one or moreprotocols. For example, the software code 1825 may control the processor1823 to perform one or more layers of the radio interface protocol.

The present disclosure may be applied to various future technologies,such as AI, robots, autonomous-driving/self-driving vehicles, and/orextended reality (XR).

<AI>

AI refers to artificial intelligence and/or the field of studyingmethodology for making it. Machine learning is a field of studyingmethodologies that define and solve various problems dealt with in AI.Machine learning may be defined as an algorithm that enhances theperformance of a task through a steady experience with any task.

An artificial neural network (ANN) is a model used in machine learning.It can mean a whole model of problem-solving ability, consisting ofartificial neurons (nodes) that form a network of synapses. An ANN canbe defined by a connection pattern between neurons in different layers,a learning process for updating model parameters, and/or an activationfunction for generating an output value. An ANN may include an inputlayer, an output layer, and optionally one or more hidden layers. Eachlayer may contain one or more neurons, and an ANN may include a synapsethat links neurons to neurons. In an ANN, each neuron can output asummation of the activation function for input signals, weights, anddeflections input through the synapse. Model parameters are parametersdetermined through learning, including deflection of neurons and/orweights of synaptic connections. The hyper-parameter means a parameterto be set in the machine learning algorithm before learning, andincludes a learning rate, a repetition number, a mini batch size, aninitialization function, etc. The objective of the ANN learning can beseen as determining the model parameters that minimize the lossfunction. The loss function can be used as an index to determine optimalmodel parameters in learning process of ANN.

Machine learning can be divided into supervised learning, unsupervisedlearning, and reinforcement learning, depending on the learning method.Supervised learning is a method of learning ANN with labels given tolearning data. Labels are the answers (or result values) that ANN mustinfer when learning data is input to ANN. Unsupervised learning can meana method of learning ANN without labels given to learning data.Reinforcement learning can mean a learning method in which an agentdefined in an environment learns to select a behavior and/or sequence ofactions that maximizes cumulative compensation in each state.

Machine learning, which is implemented as a deep neural network (DNN)that includes multiple hidden layers among ANN, is also called deeplearning. Deep learning is part of machine learning. In the following,machine learning is used to mean deep learning.

FIG. 19 shows an example of an AI device to which the technical featuresof the present disclosure can be applied.

The AI device 1900 may be implemented as a stationary device or a mobiledevice, such as a TV, a projector, a mobile phone, a smartphone, adesktop computer, a notebook, a digital broadcasting terminal, a PDA, aPMP, a navigation device, a tablet PC, a wearable device, a set-top box(STB), a digital multimedia broadcasting (DMB) receiver, a radio, awashing machine, a refrigerator, a digital signage, a robot, a vehicle,etc.

Referring to FIG. 19, the AI device 1900 may include a communicationpart 1910, an input part 1920, a learning processor 1930, a sensing part1940, an output part 1950, a memory 1960, and a processor 1970.

The communication part 1910 can transmit and/or receive data to and/orfrom external devices such as the AI devices and the AI server usingwire and/or wireless communication technology. For example, thecommunication part 1910 can transmit and/or receive sensor information,a user input, a learning model, and a control signal with externaldevices. The communication technology used by the communication part1910 may include a global system for mobile communication (GSM), a codedivision multiple access (CDMA), an LTE/LTE-A, a 5G, a WLAN, a WI-FI,BLUETOOTH, radio frequency identification (RFID), infrared dataassociation (IrDA), ZIGBEE, and/or near field communication (NFC).

The input part 1920 can acquire various kinds of data. The input part1920 may include a camera for inputting a video signal, a microphone forreceiving an audio signal, and a user input part for receivinginformation from a user. A camera and/or a microphone may be treated asa sensor, and a signal obtained from a camera and/or a microphone may bereferred to as sensing data and/or sensor information. The input part1920 can acquire input data to be used when acquiring an output usinglearning data and a learning model for model learning. The input part1920 may obtain raw input data, in which case the processor 1970 or thelearning processor 1930 may extract input features by preprocessing theinput data.

The learning processor 1930 may learn a model composed of an ANN usinglearning data. The learned ANN can be referred to as a learning model.The learning model can be used to infer result values for new input datarather than learning data, and the inferred values can be used as abasis for determining which actions to perform. The learning processor1930 may perform AI processing together with the learning processor ofthe AI server. The learning processor 1930 may include a memoryintegrated and/or implemented in the AI device 1900. Alternatively, thelearning processor 1930 may be implemented using the memory 1960, anexternal memory directly coupled to the AI device 1900, and/or a memorymaintained in an external device.

The sensing part 1940 may acquire at least one of internal informationof the AI device 1900, environment information of the AI device 1900,and/or the user information using various sensors. The sensors includedin the sensing part 1940 may include a proximity sensor, an illuminancesensor, an acceleration sensor, a magnetic sensor, a gyro sensor, aninertial sensor, an RGB sensor, an IR sensor, a fingerprint recognitionsensor, an ultrasonic sensor, an optical sensor, a microphone, a lightdetection and ranging (LIDAR), and/or a radar.

The output part 1950 may generate an output related to visual, auditory,tactile, etc. The output part 1950 may include a display unit foroutputting visual information, a speaker for outputting auditoryinformation, and/or a haptic module for outputting tactile information.

The memory 1960 may store data that supports various functions of the AIdevice 1900. For example, the memory 1960 may store input data acquiredby the input part 1920, learning data, a learning model, a learninghistory, etc.

The processor 1970 may determine at least one executable operation ofthe AI device 1900 based on information determined and/or generatedusing a data analysis algorithm and/or a machine learning algorithm. Theprocessor 1970 may then control the components of the AI device 1900 toperform the determined operation. The processor 1970 may request,retrieve, receive, and/or utilize data in the learning processor 1930and/or the memory 1960, and may control the components of the AI device1900 to execute the predicted operation and/or the operation determinedto be desirable among the at least one executable operation. Theprocessor 1970 may generate a control signal for controlling theexternal device, and may transmit the generated control signal to theexternal device, when the external device needs to be linked to performthe determined operation. The processor 1970 may obtain the intentioninformation for the user input and determine the user's requirementsbased on the obtained intention information. The processor 1970 may useat least one of a speech-to-text (STT) engine for converting speechinput into a text string and/or a natural language processing (NLP)engine for acquiring intention information of a natural language, toobtain the intention information corresponding to the user input. Atleast one of the STT engine and/or the NLP engine may be configured asan ANN, at least a part of which is learned according to a machinelearning algorithm. At least one of the STT engine and/or the NLP enginemay be learned by the learning processor 1930 and/or learned by thelearning processor of the AI server, and/or learned by their distributedprocessing. The processor 1970 may collect history information includingthe operation contents of the AI device 1900 and/or the user's feedbackon the operation, etc. The processor 1970 may store the collectedhistory information in the memory 1960 and/or the learning processor1930, and/or transmit to an external device such as the AI server. Thecollected history information can be used to update the learning model.The processor 1970 may control at least some of the components of AIdevice 1900 to drive an application program stored in memory 1960.Furthermore, the processor 1970 may operate two or more of thecomponents included in the AI device 1900 in combination with each otherfor driving the application program.

FIG. 20 shows an example of an AI system to which the technical featuresof the present disclosure can be applied.

Referring to FIG. 20, in the AI system, at least one of an AI server2020, a robot 2010 a, an autonomous vehicle 2010 b, an XR device 2010 c,a smartphone 2010 d and/or a home appliance 2010 e is connected to acloud network 2000. The robot 2010 a, the autonomous vehicle 2010 b, theXR device 2010 c, the smartphone 2010 d, and/or the home appliance 2010e to which the AI technology is applied may be referred to as AI devices2010 a to 2010 e.

The cloud network 2000 may refer to a network that forms part of a cloudcomputing infrastructure and/or resides in a cloud computinginfrastructure. The cloud network 2000 may be configured using a 3Gnetwork, a 4G or LTE network, and/or a 5G network. That is, each of thedevices 2010 a to 2010 e and 2020 consisting the AI system may beconnected to each other through the cloud network 2000. In particular,each of the devices 2010 a to 2010 e and 2020 may communicate with eachother through a base station, but may directly communicate with eachother without using a base station.

The AI server 2020 may include a server for performing AI processing anda server for performing operations on big data. The AI server 2020 isconnected to at least one or more of AI devices constituting the AIsystem, i.e. the robot 2010 a, the autonomous vehicle 2010 b, the XRdevice 2010 c, the smartphone 2010 d and/or the home appliance 2010 ethrough the cloud network 2000, and may assist at least some AIprocessing of the connected AI devices 2010 a to 2010 e. The AI server2020 can learn the ANN according to the machine learning algorithm onbehalf of the AI devices 2010 a to 2010 e, and can directly store thelearning models and/or transmit them to the AI devices 2010 a to 2010 e.The AI server 2020 may receive the input data from the AI devices 2010 ato 2010 e, infer the result value with respect to the received inputdata using the learning model, generate a response and/or a controlcommand based on the inferred result value, and transmit the generateddata to the AI devices 2010 a to 2010 e. Alternatively, the AI devices2010 a to 2010 e may directly infer a result value for the input datausing a learning model, and generate a response and/or a control commandbased on the inferred result value.

Various embodiments of the AI devices 2010 a to 2010 e to which thetechnical features of the present disclosure can be applied will bedescribed. The AI devices 2010 a to 2010 e shown in FIG. 20 can be seenas specific embodiments of the AI device 1100 shown in FIG. 11.

The present disclosure can have various advantageous effects.

For example, by transmitting an updated mobility command includingupdated configuration parameters and excluding configuration parametersincluded in a previously transmitted mobility command (i.e.,configuration parameters that are not updated or remain the same), thenetwork can send a mobility command of reduced sized to the wirelessdevice, in particular when multiple target cells are configured forconditional mobility.

For example, it is beneficial to reduce signalling overhead in case whenmultiple target cells are configured for conditional mobility or whenconditional mobility command is updated that the network transmits anupdated mobility command including updated configuration parameters andexcluding configuration parameters included in a previously transmittedmobility command (i.e., configuration parameters that are not updated orremain the same).

Advantageous effects which can be obtained through specific embodimentsof the present disclosure are not limited to the advantageous effectslisted above. For example, there may be a variety of technical effectsthat a person having ordinary skill in the related art can understandand/or derive from the present disclosure. Accordingly, the specificeffects of the present disclosure are not limited to those explicitlydescribed herein, but may include various effects that may be understoodor derived from the technical features of the present disclosure.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope of the present disclosure.

Claims in the present description can be combined in a various way. Forinstance, technical features in method claims of the present descriptioncan be combined to be implemented or performed in an apparatus, andtechnical features in apparatus claims can be combined to be implementedor performed in a method. Further, technical features in method claim(s)and apparatus claim(s) can be combined to be implemented or performed inan apparatus. Further, technical features in method claim(s) andapparatus claim(s) can be combined to be implemented or performed in amethod. Other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A method performed by a wireless device in awireless communication system, the method comprising: receiving a firstmobility command related to a first identity; updating, based on thefirst mobility command, a list of one or more mobility commands storedin the wireless device in association with a corresponding identity,wherein each mobility command in the list of one or more mobilitycommands comprises a corresponding mobility condition and acorresponding random access configuration; identifying a mobilitycommand, in the list of one or more mobility commands, in which amobility condition is satisfied for a target cell; and performing amobility towards the target cell by applying the identified mobilitycommand, wherein the updating of the list of one or more mobilitycommands comprises; based on that the first identity matches a secondidentity related to a second mobility command in the list of one or moremobility commands, replacing one or more parameter values in the secondmobility command with one or more parameter values in the first mobilitycommand; and based on that the first identity is different from anidentity related to any mobility command in the list of one or moremobility commands, adding the first mobility command in association withthe first identity to the list of one or more mobility commands.
 2. Themethod of claim 1, wherein each mobility command is related to acorresponding candidate target cell.
 3. The method of claim 1, furthercomprising updating the second mobility command based on the firstmobility command, wherein the first mobility command includes parametervalues of at least one first entry that are updated from those of the atleast one first entry in the second mobility command, and excludesparameter values of at least one second entry that are included in thesecond mobility command.
 4. The method of claim 3, wherein the updatingof the second mobility command based on the first mobility commandcomprises: identifying, in the second mobility command, the parametervalues of the at least one second entry that are excluded in the firstmobility command; and adding the parameter values of the at least onesecond entry to the first mobility command to obtain an updated versionof the second mobility command.
 5. The method of claim 3, wherein theupdating of the second mobility command based on the first mobilitycommand comprises: replacing the parameter values of the at least onefirst entry in the second mobility command with those of the at leastone first entry in the first mobility command to obtain an updatedversion of the second mobility command.
 6. The method of claim 1,further comprising: upon identifying that the target cell satisfies ahandover condition for the target cell, performing a handover to thetarget cell.
 7. The method of claim 1, wherein the wireless device is incommunication with a master node (MN) and a secondary node (SN) in adual connectivity (DC), and wherein the method further comprises: uponidentifying that the target cell satisfies a SN change condition for thetarget cell, performing a SN change from the SN to another SN related tothe target cell.
 8. The method of claim 1, further comprising: uponidentifying that the target cell satisfies a secondary node (SN)addition condition for the target cell, performing a SN addition for aradio access network (RAN) node related to the target cell.
 9. Themethod of claim 1, further comprising: identifying, among identities inthe list of one or more mobility commands, one or more identities forwhich mobility conditions are satisfied; identifying one or morecandidate target cells related to one or more mobility commands havingthe one or more identities; and selecting the target cell among the oneor more candidate target cells for a mobility.
 10. The method of claim9, further comprising: identifying a handover command of the targetcell; and applying parameter values in the handover command of thetarget cell to perform a handover to the target cell.
 11. The method ofclaim 9, wherein the wireless device is in communication with a masternode (MN) and a secondary node (SN) in a dual connectivity (DC), furthercomprising: identifying a SN change command of the target cell; andapplying parameter values in the SN change command of the target cell toperform a SN change from the SN to another SN related to the targetcell.
 12. The method of claim 9, further comprising: identifying asecondary node (SN) addition command of the target cell; and applyingparameter values in the SN addition command of the target cell toperform a SN addition for a radio access network (RAN) node related tothe target cell.
 13. The method of claim 1, wherein the wireless deviceis in communication with at least one of a user equipment, a network, oran autonomous vehicle other than the wireless device.
 14. A wirelessdevice in a wireless communication system comprising: a transceiver; amemory; and at least one processor operatively coupled to thetransceiver and the memory, and configured to: control the transceiverto receive a first mobility command related to a first identity update,based on the first mobility command, a list of one or more mobilitycommands stored in the wireless device in association with acorresponding identity, wherein each mobility command in the list of oneor more mobility commands comprises a corresponding mobility conditionand a corresponding random access configuration: identify a mobilitycommand, in the list of one or more mobility commands, in which amobility condition is satisfied for a target cell; and perform amobility towards the target cell by applying the identified mobilitycommand, wherein the updating of the list of one or more mobilitycommands comprises: based on that the first identity matches a secondidentity related to a second mobility command in the list of one or moremobility commands, replacing one or more parameter values in the secondmobility command with one or more parameter values in the first mobilitycommand: and based on that the first identity is different from anidentity related to any mobility command in the list of one or moremobility commands, adding the first mobility command in association withthe first identity to the list of one or more mobility commands.